"In the sessions that we had, there was no specific mention of a date. I think they got our message through," Gates told reporters on a flight back to Washington after talks in Ankara.

Asked what made him think that, he said with a laugh: "Because they heard it four times."

Gates met separately with President Abdullah Gul, Prime Minister Recep Tayyip Erdogan, Defence Minister Vecdi Gonul and chief of the general staff General Yasar Buyukanit to press for a quick end to the week-old offensive against Kurdistan Workers's Party (PKK) rebels operating from northern Iraq.

"They made it clear they believe it is in their interest to accomplish this operation quickly. But they also wish to accomplish the objectives they set out to," said Geoff Morrell, the Pentagon press secretary.

Morrell described the sessions as businesslike and serious but conducted in an atmosphere that reflected the close relationship between the two NATO allies.

The United States has provided the Turks with near-realtime intelligence on the PKK that has been crucial to their military operations.

Gates said earlier after meeting with Gonul that it would not advance US interest to threaten to cut off the flow of intelligence.

Asked about the intelligence link on the flight home, Gates said: "It did not come up. I did not raise it."

In each session, Gates said he urged Turkey to deepen its dialogue with the Iraqis, to be more open about the scope of the operation, and the importance of recognising military force along will not solve the problem.

He emphasized the need for political, economic and social initiatives aimed at taking away Kurdish support for the PKK, which is listed as a terrorist organization by Turkey, the United States and European Union.

Gates told Turkish leaders that providing more information about the numbers of troops involved, and the limited area in which the operation was taking place "would help correct a lot of misimpressions and potential misunderstandings."

"Based on what they told me it sounds like the size of the operation is probably proportionate," Gates said.

"They described the operation, and the president and prime minister in particular, described some of the initiatives they have taken in a non-military arena," he said.

"And their concern is finding the balance in terms of how much they can say publicly without compromising their military operations, particularly in the context of timing.

"They've clearly reached out to the Iraqis -- they just had a special mission return late last night from Baghdad -- so I think they are beginning that part of the process," Gates said.