The two leaders spoke on the phone Thursday, after Ankara threatened a cross-border operation if Washington and Baghdad fail to crack down on the separatist Kurdistan Workers' Party (PKK) in northern Iraq.

The warning followed a series of security meetings in Ankara after the killing last week of 15 security force members by PKK militants.

"I told him (Bush) we want to cooperate with the Iraqi government and he said he agrees we should work together on this issue," Erdogan told reporters late Thursday during a visit to northern Cyprus, the Anatolia news agency reported.

"But I also told him that the limits of our tolerance have been seriously breached and we cannot just put aside the fact that we had 15 martyrs in three days," Erdogan said.

Like Ankara, Washington considers the PKK a terror organization and has pledged support to its NATO ally Turkey in combating the group.

But it has been reluctant to crack down on the PKK in northern Iraq, arguing that allied forces are overwhelmed by violence in other parts of the country and that military action in the north could destabilize the relatively calm Kurdish-populated region.

Washington has warned Turkey against unilateral cross-border action, drawing angry accusations from Erdogan that it is using double standards in the region -- a reference to US support for Israeli offensives against Islamist militants in Lebanon and the Gaza Strip.

Thousands of PKK militants have moved to northern Iraq since 1999, when the group declared a unilateral ceasefire after the capture of its leader Abdullah Ocalan, now serving a life sentence for treason.

The truce was called off in June 2004 and violence has markedly escalated since in mainly Kurdish-populated southeastern Turkey.

Ankara says PKK militants use mountain bases in northern Iraq as a springboard for attacks inside Turkey, enjoy unrestricted movement in the Kurdish-run enclave and are able to easily obtain weapons and explosives there.

At least 87 PKK rebels and 51 members of the security forces have died in escalating unrest in southeast Turkey this year, according to an AFP count.

Kurdish militants also claimed responsibility for 11 bomb attacks in urban centres, in which nine people were killed and nearly 140 injured.