Pentagon officials are now starting to say publicly that the U.S. is flying manned spy planes over the border area, providing Turkey with more intelligence information, and that there are standing orders for American forces to capture rebels they find.
CBS News national security correspondent David Martin reported last Friday thatto gather intelligence on Kurdish terrorists.
But the U.S. commander in northern Iraq, Army Maj. Gen. Benjamin Mixon, told Martin that he planned to do "absolutely nothing" to counter Kurdish rebels operating from the region.
The top American commander in Iraq, in comments that appeared aimed at allaying Turkish frustration over the matter, said Sunday the U.S. military was playing a role in trying to defuse tensions.
Gen. David Petraeus declined to elaborate. Since then, however, Pentagon officials have detailed a number of examples to undermine the rebels of the Kurdistan Workers' Party, or PKK, holed up in bases in northern Iraq.
"We are assisting the Turks in their efforts to combat the PKK by supplying them with intelligence, lots of intelligence," Defense Department press secretary Geoff Morrell said.
He said 10 members of the PKK - which the U.S. considers a terrorist organization - are in a U.S. "most-wanted" database. That means American forces have had standing orders for some time to pick them up if they are found.
In Iraq, Foreign Minister Hoshyar Zebari said Baghdad would ensure there were more checkpoints along its northern border to halt shipments of fuel, food and other supplies to Kurdish insurgents. Zebari, a Kurd, said Iraq would also take other, unspecified measures to hinder PKK cross-border operations.
The assurances from the U.S. and Iraq came after Turkish Prime Minister Recep Tayyip Erdogan accused Massoud Barzani, the leader of Iraq's semiautonomous Kurdish region, of "aiding and abetting" the rebels, in a sign of growing frustration with Iraqi Kurds' refusal to crack down on them.
Turkey fears that Iraqi Kurds could set up an independent Kurdish state - Barzani has set that as his ultimate goal - in a move that could fuel separatist sentiments within Turkey.
Erdogan planned to meet Friday in Turkey with Secretary of State Condoleezza Rice.
Turkey has complained for months about what it contends is a lack of U.S. support against the PKK. The Turkish government has threatened a full-scale ground attack into northern Iraq if the U.S. and Iraqi officials fail to do something about the rebels.
"We have given them more and more intelligence as a result of the recent concerns. ... There has been an increased level of intelligence sharing," Morrell told reporters.
He did not say when the stepped-up cooperation began or how the intelligence was being gathered. But the military in the last week or so has sent manned U-2 spy planes to areas used by rebels and is providing reconnaissance on the border, a defense official said.
The official spoke on condition of anonymity because he was not authorized to discuss the matter publicly.
The official also said the U.S. military saw a battalion of several hundred Peshmerga - the militia of the Kurdish Iraqi regional authorities - move toward the border over the weekend.
Top Defense Department and State Department officials have said that Iraq's Kurdish regional government should cut rebel supplies and disrupt rebel movement over the border, and that Washington is frustrated by Kurdish inaction.
Defense Secretary Robert Gates suggested last week that airstrikes or major ground assaults by U.S., Turkish, or other forces would not help much because not enough is known about where the rebels are at a given time.
The U.S. and Iraqi governments have urged Turkey not to send troops across the border and are promoting a diplomatic solution. They fear a large military operation, opening a new front in the Iraq war, would unsettle what is now the most stable part of the country.
A Turkish incursion would also put the United States in an awkward position involving NATO-member Turkey, the Baghdad government and the self-governing Iraqi Kurds in the north.
Turkey's prime minister, Erdogan, said this week that it was "unavoidable that Turkey will have to go through a more intensive military process" to counter the rebels. Turkish forces have been shelling rebel positions near the border.
Erdogan plans talks with President Bush next week in Washington.
"We expect the Iraqis to step up and make sure that they are doing everything they can to eradicate the PKK," White House press secretary Dana Perino said Wednesday.
"Turkey has a right to defend its people, it has a right to look for its soldiers, and we are asking Turkey, as well, to exercise restraint and to limit its exercises to the PKK. And so far that's continuing to work, but it takes a lot of dialogue and discussions," she said.