(CNN) -- President Obama said Thursday that watching the arrival of 18 flag-draped cases containing bodies of Americans killed in Afghanistan was a "sobering reminder" of U.S. sacrifice as he prepares to decide on sending more troops there.



At a brief media appearance with visiting Minister Mentor Lee Kuan Yew of Singapore, Obama was asked whether his unannounced appearance at Dover Air Force Base in Delaware for the pre-dawn dignified transfer of the bodies would influence his decision on troop levels in Afghanistan.



"Obviously, it was a sobering reminder of the extraordinary sacrifices that our young men and women in uniform are engaging in every single day," the president said.



Obama said the burden of war on U.S. troops and their families will "bear on how I see these conflicts."



"It is something I think about each and every day," he said.



Also in attendance for the transfer of the bodies were Attorney General Eric Holder and Michele Leonhart, acting administrator of the Drug Enforcement Administration.



The bodies included three DEA special agents and 15 U.S. troops who died in Afghanistan this week.



The agents were killed Monday as they returned from a raid on a compound believed to be harboring insurgents tied to drug trafficking. Seven U.S. troops also died when their helicopter went down in western Afghanistan.



The military transport that landed in Delaware also included the bodies of eight U.S. soldiers killed Tuesday when their vehicles were hit by roadside bombs in two incidents in southern Afghanistan.



The soldiers were from the 5th Stryker Brigade Combat Team of the 2nd Infantry Division, based at Fort Lewis, Washington.



The DEA identified the agents killed Monday as Forrest N. Leamon, 37, of Woodbridge, Virginia; Chad L. Michael, 30, of Quantico, Virginia; and Michael E. Weston, 37, of Washington.



Leamon and Michael were members of the DEA's Foreign-deployed Advisory and Support Teams, and Weston was assigned to the agency's Kabul office.



CNN's Carol Cratty contributed to this report.
Who were killed by roadside bomb in Afghanistan? How many soldiers die Who were recently killed in helicopter crash? What did the US troops die of? What was on hand of Obama? who was recently killed?
eight U.S. soldiers 18 Seven U.S. troops hit by roadside bombs "sobering reminder" three DEA special agents and 15 U.S. troops
question: Who were killed by roadside bomb in Afghanistan?, answer: eight U.S. soldiers | question: How many soldiers die, answer: 18 | question: Who were recently killed in helicopter crash?, answer: Seven U.S. troops | question: What did the US troops die of?, answer: hit by roadside bombs | question: What was on hand of Obama?, answer: "sobering reminder" | question: who was recently killed?, answer: three DEA special agents and 15 U.S. troops