WASHINGTON (CNN) -- American U2 reconnaissance planes have been flying over the Turkey-Iraq border to observe military movements, said three U.S. military sources Wednesday.



A Turkish army convoy heads toward the Turkey-Iraq border on Monday.



Word of the flights comes a day before top-level meetings between U.S. and Turkish government officials and prior to a regional conference aimed at easing tensions between Ankara and Kurdish rebels across Turkey's border with Iraq.



Turkey -- which shares its Incirlik air base with U.S. forces -- is a key member of  NATO and acts as a vital conduit for U.S. military supplies.



Pentagon spokesman Geoff Morrell confirmed Wednesday that U.S. military and intelligence communities are sharing information with Turkey to help them fight members of the Kurdistan Workers' Party, or PKK, who have made cross-border attacks.  See location of key U.S.-Turkish air base »



"We are assisting by supplying them, the Turks, with intelligence, lots of intelligence," said Morrell. "There has been an increased level" of intelligence sharing.



Turkey has urged Washington to offer more support against the rebels and Ankara has threatened to launch a full-scale offensive if Iraqi and Kurdish officials fail to neutralize the PKK. U.S. and Iraqi diplomats have been working to restrain Turkey from such a response. Recent limited fighting in southeastern Turkey has spilled into northern Iraq.



During operations near the border on Monday, Turkish forces fired on suspected rebel positions.  Watch Turkish helicopters fire on rebels »



On Thursday, U.S. Secretary of State Condoleezza Rice is set to meet with Turkish officials in Ankara and President Bush holds talks in Washington with Turkish Prime Minister Recep Tayyip Erdogan.



Also, a conference of regional officials, including Iraq, is scheduled Thursday and Friday in Istanbul.



Iranian Foreign Minister Manouchehr Mottaki has joined efforts to ease cross-border tensions. Mottaki met in Iraq Wednesday with his Iraqi counterpart, Hoshyar Zebari, and Iraqi Prime Minister Nuri al-Maliki.



Mottaki's involvement prompted him to delay a scheduled visit to Lebanon, according to Iran's Islamic Republic News Agency, which quoted Iranian Ambassador to Lebanon Mohammad Reza Sheibani.



Iran's foreign minister is offering his "full support" to the regional conference in Istanbul, said a statement from al-Maliki's office. The statement also said Mottaki wants to help "solve the border crisis between Turkey and the PKK."



Earlier this month, proposed legislation in the U.S. Congress prompted Turkey to threaten to restrict U.S. access to Turkish airspace or cut off access to the air base at Incirlik. Some lawmakers wanted a vote on legislation that would have officially declared that the killing of Armenians by Ottoman Turks in World War I was "genocide."



Turkey recalled its ambassador to the United States and warned of repercussions in the growing dispute.



Sponsors of the congressional resolution have asked for a delay in the vote. E-mail to a friend
What has Turkey threatened? Who is observing military movements? What is there an increased level of? Who is meeting with Turk officials? Who has threatened full scale attack?
to launch a full-scale offensive if Iraqi and Kurdish officials fail to neutralize the PKK. American U2 reconnaissance planes intelligence sharing. Condoleezza Rice Ankara
question: What has Turkey threatened?, answer: to launch a full-scale offensive if Iraqi and Kurdish officials fail to neutralize the PKK. | question: Who is observing military movements?, answer: American U2 reconnaissance planes | question: What is there an increased level of?, answer: intelligence sharing. | question: Who is meeting with Turk officials?, answer: Condoleezza Rice | question: Who has threatened full scale attack?, answer: Ankara