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 / Updated By Ken Dilanian, Alex Johnson and Corky Siemaszko 
 
 The National Archives published nearly 3,000 previously sealed or censored documents related to the assassination of President John F. Kennedy on Thursday, but the White House said it was delaying the release of others. 
 
 Under a 1992 law inspired by the conspiracist movie "JFK," the National Archives was supposed to have released all of the remaining records by midnight ET — unless President Donald Trump objected on national security grounds. 
 
 In the end, the president allowed the release of 2,891 of at least 3,140 documents, with the rest subject to a 180-day review of redactions from objecting agencies. The White House said later that the remaining records would be released "on a rolling basis in the coming weeks." 
 
 "I am ordering today that the veil finally be lifted," Trump wrote in a memo announcing the delay Thursday evening. 
 
 "At the same time, executive departments and agencies have proposed to me that certain information should continue to be redacted because of national security, law enforcement, and foreign affairs concerns," he wrote. "I have no choice — today — but to accept those redactions rather than allow potentially irreversible harm to our Nation's security." 
 
 Still, he warned that agency heads should be "extremely circumspect" in asking for further postponing the release of any of the documents, saying: "The need for continued protection can only have grown weaker with the passage of time." 
 
 President John F. Kennedy's motorcade in Dallas on Nov. 22, 1963. Newseum / PRNewsfoto file 
 
 Trump "wants to ensure there is full transparency here," a senior administration official said at a briefing. He is "expecting agencies to do a better job in reducing conflict within redactions and get this information out as quickly as possible." 
 
 The CIA said in a statement that the redactions were meant to protect information that would "harm national security — including the names of CIA assets and current and former CIA officers, as well as specific intelligence methods and partnerships that remain viable to protecting the nation today." 
 
 "Every single one of the approximately 18,000 remaining CIA records in the collection will ultimately be released, with no document withheld in full," the agency said. 
 
 Trump, no stranger to conspiracy theories about the Kennedy killing, had appeared eager to get the latest JFK documents out. 
 
 The long anticipated release of the #JFKFiles will take place tomorrow. So interesting! — Donald J. Trump (@realDonaldTrump) October 25, 2017 
 
 As journalists, scholars and assassination buffs began scouring the thousands of pages Thursday night, it remained to be seen whether the document dump would satisfy the many people who still dispute the finding of the Warren Commission that Lee Harvey Oswald acted alone when he gunned down Kennedy on Nov. 22, 1963. 
 
 The assassination shocked the nation and spawned a conspiracy industry that continues to pump out alternative theories about who was really behind the killing. 
 
 Officials at the National Archives made a point of trying to tamp down expectations that the newest batch of documents contains any blockbuster revelations — and they have noted repeatedly that about 90 percent of the available records related to the assassination are already public. 
 
 Related: What Could Be in the New Kennedy Assassination Records? 
 
 Clint Hill, the Secret Service agent who used his body to shield the mortally wounded president and first lady Jacqueline Kennedy after the first shots rang out in Dallas, said earlier Thursday that he hoped the latest declassified papers shed light on why Oswald pulled the trigger. 
 
 "I'm hoping that within that material — and there's lots of it — there will be some indication as to the motive, the reason why he did what he did," Hill told MSNBC. 
 
 Hill said he still blames himself for not having reacted faster when the presidential motorcade came under fire. 
 
 "Deep down, I still have that sense of guilt that I should have been able to get there quicker and I didn't," he said. "I was the only one who had a chance to do anything." 
 
 The paperwork that was scheduled to be unveiled on Thursday has already been vetted by the Assassination Records Review Board, a panel created in the aftermath of Oliver Stone's 1991 conspiracy film "JFK," which popularized the notion that Kennedy was killed by rogue FBI and CIA agents. 
 
 The ARRB released the bulk of the JFK assassination paperwork two years after it was founded. The new documents were marked "NBR," or Not Believed Relevant, the panel's chairman, John Tunheim, said in March at a National Press Club conference in Washington. 
 
 "It's not that important to keep protecting it," he said. Still, he added, "I think there will be stuff interesting to researchers." 
 
 PHOTOS: JFK Assassination: The Day the President Was Shot 
 
 About 200 pages of the new batch are expected to delve into the six-day visit that Oswald, a onetime Marine who had defected to the Soviet Union, made to Mexico City just before Kennedy's assassination. One of the juiciest stories is likely to be that of June Cobb, a CIA spy working in Cuba and Mexico, who reported that Oswald had been spotted in Mexico City. 
 
 Cobb, born Viola June Cobb in Ponca City, Oklahoma, died Oct. 17, 2015, in New York, where she was living in a Manhattan senior center, an official there and her former sister-in-law told NBC News. 
 
 Tunheim said in March that the CIA, the State Department and other federal agencies balked at releasing the Mexico City paperwork "because it was thought to be detrimental to our relationship with the Mexican government at the time." ||||| The nation’s conspiracy-theorist-in-chief is facing a momentous decision. Will President Donald Trump allow the public to see a trove of thousands of long-secret government files about the event that, more than any other in modern American history, has fueled conspiracy theories – the 1963 assassination of President John F. Kennedy? 
 
 The answer must come within months. And, according to a new timeline offered by the National Archives, it could come within weeks. 
 
 Story Continued Below 
 
 Under the deadline set by a 1992 law, Trump has six months left to decide whether he will block the release of an estimated 3,600 files related to the assassination that are still under seal at the Archives. From what is known of the JFK documents, most come from the CIA and FBI, and a number may help resolve lingering questions about whether those agencies missed evidence of a conspiracy in Kennedy’s death. As with every earlier release of JFK assassination documents in the 53 years since shots rang out in Dealey Plaza in Dallas, it is virtually certain that some of the files will be seized on to support popular conspiracy theories about Kennedy’s murder; other documents are likely to undermine them. 
 
 There is no little irony in the fact that decision will be left to Trump, long a promoter of so many baseless conspiracy theories about everything from his predecessor’s birthplace to the notion that the father of one of his campaign-trail rivals was in league with JFK assassin Lee Harvey Oswald. 
 
 For the first time, the Trump White House is acknowledging that it is focused on the issue, even if it offers no hint about what the President will do. A White House official, speaking on condition of anonymity, told Politico last week that the Trump administration “is familiar with the requirements” of the 1992 law and that White House is working with the National Archives “to enable a smooth process in anticipation of the October deadline.” 
 
 Under the 1992 JFK Assassination Records Collection Act, the library of documents about Kennedy’s death must be made public in full by the deadline of this October 26, the law’s 25th anniversary, unless Trump decides otherwise. It is his decision alone. 
 
 The prospect of the release of the last of the government’s long-secret JFK assassination files has long tantalized historians and other scholars, to say nothing of the nation’s armies of conspiracy theorists, since no one can claim to know exactly what is in there. 
 
 Martha W. Murphy, the Archives official who oversees the records, said in an interview last month that a team of researchers with high-level security clearances is at work to prepare the JFK files for release and hopes to begin unsealing them in batches much earlier than October – possibly as early as summer. 
 
 Beyond releasing the 3,600 never-before-seen JFK files, the Archives is reviewing another 35,000 assassination-related documents, previously released in part, so they can be unsealed in full. Short of an order from the president, Murphy said, the Archives is committed to making everything public this year: “There’s very little decision-making for us.” 
 
 Many of the documents are known to come from the files of CIA officials who monitored a mysterious trip that Oswald paid to Mexico City several weeks before the assassination – a trip that brought Kennedy’s future killer under intense surveillance by the spy agency as he paid visits to both the Soviet and Cuban embassies there. The CIA said it monitored all visitors to the embassies and opened surveillance of Oswald as soon as he was detected inside the Soviet compound for the first time. 
 
 Other documents are known to identify, by name, American and foreign spies and law-enforcement sources who had previously been granted anonymity for information about Oswald and the assassination. At least 400 pages of the files involve E. Howard Hunt, the former CIA operative turned Watergate conspirator who claimed on his deathbed that he had advance knowledge of Kennedy’s murder. 
 
 The documents were gathered together by a temporary federal agency, the Assassination Records Review Board, that was established under the 1992 law. In an interview last month, its former chairman, Judge John R. Tunheim of the Federal District Court in Minnesota, said he “wouldn’t be surprised if there’s something important” in the documents, especially given how much of the history of the Kennedy assassination has had to be rewritten in recent decades. 
 
 He said he knew of “no bombshells” in the files when the board agreed to keep them secret two decades ago, but names, places and events described in the documents could have significance now, given what has been learned about the assassination since the board went out of business. “Today, with a broader understanding of history, certain things may be far more relevant,” he said. 
 
 Murphy, the Archives official, said she, too, knew of no shocking information in the documents – but she said her researchers were not in a position to judge their significance. “As you can imagine, we’re not reading them for that, so we’re probably not the best people to tell you,” she said. “I will say this: This collection is really interesting as a snapshot of the Cold War.” 
 
 The Review Board, created by Congress to show transparency in response to the public furor created by Oliver Stone’s conspiracy-minded 1991 film “JFK,” did force the release of a massive library of other long-secret documents from the CIA, FBI, Secret Service and other federal agencies, as well as from congressional investigations of the assassination. 
 
 Many showed how much evidence was withheld from the Warren Commission, the independent panel led by Chief Justice Earl Warren that investigated the assassination and concluded in 1964 that there was no evidence of a conspiracy in Kennedy’s death. 
 
 The documents showed that both the CIA and FBI had much more extensive information about Oswald—and the danger he posed to JFK—before the assassination than the agencies admitted to Warren’s investigation. The evidence appeared to have been withheld from the commission out of fear that it would expose how the CIA and FBI had bungled the opportunity to stop Oswald. 
 
 Under the 1992 law, agencies may make a final appeal to try to stop the unsealing of specific documents on national security grounds. But the law grants only one person the power to actually block the release: the president. The law allows Trump to keep a document secret beyond the 25-year deadline if he certifies to the National Archives that secrecy was “made necessary by an identifiable harm to military defense, intelligence operations, law enforcement or conduct of foreign relations” and that “the identifiable harm is of such gravity that it outweighs the public interest in disclosure.” 
 
 Both the CIA and FBI acknowledged in written statements last month that they are reviewing the documents scheduled for release; neither agency would say if it planned to appeal to the White House to block the unsealing of any of the records. “CIA continues to review the remaining CIA documents in the collection to determine the appropriate next steps with respect to any previously-unreleased CIA information,” said agency spokesperson Heather Fritz Horniak. The FBI said it had a team of 21 researchers assigned to the document review. 
 
 According to a skeletal index of the documents prepared by the Archives, some of the files appear to involve, at least indirectly, a set of conspiracy theories that Trump himself promoted during the 2016 campaign – about possible ties between Cuban exile groups in the United States and Oswald. 
 
 On the campaign trail, Trump repeatedly promoted an article published last April in the National Enquirer that suggested a connection between Oswald and the Cuban-born father of Senator Ted Cruz of Texas, one of Trump’s rivals for the Republican nomination. The article was based entirely on a 1963 photograph that showed Oswald, a self-proclaimed Marxist and champion of Fidel Castro’s Communist revolution in Cuba, handing out pro-Castro leaflets in New Orleans with a man who, the tabloid suggested, was Cruz’s father, Rafael. 
 
 The Cruz family denied that the senator’s family was the man depicted in the photo and that Rafael Cruz had any connection to Oswald; there is no other evidence of any connection. 
 
 The National Archives index shows that the documents to be released this year include a 86-page file on a prominent CIA-backed anti-Castro exile group that Oswald appears to have tried to infiltrate in New Orleans, his hometown, in order to gather information that might be of use to the Castro government. 
 
 Judge Tunheim said that Oswald’s trip to Mexico City in September and October 1963 figures directly or indirectly in many of the documents that remain under seal, including the internal files of CIA operatives who worked at the American embassy there. 
 
 Historians agree that the trip, which Oswald apparently undertook in hopes of obtaining a visa to defect to Castro’s Cuba, much as he had once tried to defect to the Soviet Union, has never been fully investigated. 
 
 “I still think there are loose threads in Mexico City that no one has ever explored,” Tunheim said. “It was a bizarre chapter – there’s no question about it.” Previously declassified CIA and FBI documents suggest that Oswald openly boasted to Cuban officials there about his intention to kill Kennedy and that he had a brief affair with a Mexican woman who worked in Cuba’s consulate. The American ambassador to Mexico at the time of the assassination said later that he believed the woman had probably been working for the CIA. 
 
 Tunheim said the Review Board agreed to keep the Mexico-related documents secret in the 1990s at the request of the State Department, the CIA and other agencies that warned that their release could do damage to relations with the Mexico government, which worked closely with the CIA and FBI during the Cold War. “Mexico City was where everybody spied on everybody else,” the judge said. 
 
 But given the chill in relations between the United States and Mexico following Trump’s election and early moves by his administration to build its long-promised wall along the Mexican border, a similar plea to keep the documents secret may not go very far with the new president. Said Tunheim: “I guess we don’t have much of a relationship with the Mexican government to protect anymore.” 
 
 Philip Shenon, a former Washington and foreign correspondent for the New York Times, is author, most recently, of A Cruel and Shocking Act: The Secret History of the Kennedy Assassination. This essay is drawn from the afterword to the new paperback edition of the book, scheduled for publication by Picador on Feb. 3. ||||| Media playback is unsupported on your device Media caption What will top-secret JFK files tell us about Kennedy's killer? 
 
 The US government has released 2,800 previously classified files on the assassination of President John F Kennedy in 1963. 
 
 President Donald Trump said the public deserved to be "fully informed" about the event, which has been the subject of numerous conspiracy theories. 
 
 But some documents have been withheld at the request of government agencies. 
 
 One memo revealed that the FBI had warned police of a death threat against the assassin Lee Harvey Oswald. 
 
 "We at once notified the chief of police and he assured us Oswald would be given sufficient protection", writes the FBI director J Edgar Hoover. 
 
 Oswald, a former Marine and self-proclaimed Marxist, was shot dead in the basement of the Dallas Police department two days after President Kennedy was killed. 
 
 As the documents are pored over and analysed, other findings include a CIA memo that suggests Oswald spoke with a KGB officer at the Russian embassy in Mexico City. The memo says the KGB officer Oswald spoke with worked for a department "responsible for sabotage and assassination". 
 
 Another memo showed that Soviet officials feared an "irresponsible general" would launch a missile at the USSR in the wake of President Kennedy's death. 
 
 One memo tells how a British regional newspaper, the Cambridge News, received an anonymous call about "some big news" in the US, minutes before the assassination. 
 
 A copy of the memo was released by the National Archives in the US in July, but had gone unreported. 
 
 Image copyright Reuters Image caption The president and first lady in Dallas less than an hour before his assassination 
 
 President Kennedy was shot dead on 22 November 1963 as he travelled through Dallas in an open-topped limousine. 
 
 The Warren Commission's report into the shooting, published in September 1964, said that Lee Harvey Oswald had fired the fatal shots from the Texas School Book Depository building. 
 
 JFK Files: The most interesting points 
 
 There was "no evidence that either Lee Harvey Oswald or Jack Ruby was part of any conspiracy, domestic or foreign", the commission said. 
 
 A 1992 law passed by Congress required all records related to the assassination - around five million pages - to be publicly disclosed in full within 25 years. 
 
 The deadline was Thursday. 
 
 More than 90% of the files were already in the public domain. 
 
 Allegations of a government cover-up are unlikely to be assuaged by reports that the CIA, FBI, Department of State and other agencies lobbied at the last minute to keep certain documents under wraps. 
 
 In a memo directing heads of executive departments to release the files, Mr Trump said the American public deserves to be "fully informed about all aspects of this pivotal event". 
 
 "Therefore, I am ordering today that the veil finally be lifted," the president wrote. 
 
 Some redacted documents are undergoing a further six-month review, but it is possible those records could stay secret after the deadline on 26 April next year. 
 
 The president, according to White House officials, was reluctant to agree to agency requests to hold the remaining documents. 
 
 "I have no choice - today - but to accept those redactions rather than allow potentially irreversible harm to our Nation's security," Mr Trump added in his memo. 
 
 The records have been released on the National Archives website.
– The can has been kicked a little farther down the road. When President Trump in October approved the release of previously classified or redacted documents on the JFK assassination, he blocked the release of others over national security concerns and gave federal agencies 180 days to re-review the withheld documents. The review in some cases turned up "identifiable national security, law enforcement, and foreign affairs concerns," per a memo written by Trump, who on Thursday said some files would now be kept under wraps until Oct. 26, 2021. He wrote that some files are "of such gravity that it outweighs the public interest in immediate disclosure," per the AP, but he ordered that they be reviewed over the next three years, and that any that can be released be made public immediately. The Dallas Morning News reports roughly 19,000 documents were released Thursday by the National Archives—the largest batch thus far, notes the Hill; 520 remain fully sealed. In his memo, Trump included a hopeful note for the curious: "The need for continued protection can only grow weaker with the passage of time from this congressional finding." (Some were hoping files would be released this week that would shed light on a 1971 suicide.)