As Pakistan sinks deeper into political crisis, Bush will be loath to see any escalation in tensions between Turkey, another crucial anti-terror partner, and US allies in northern Iraq's autonomous Kurdish region.

Ahead of his afternoon meeting with Bush at the White House, Erdogan warned "the Turkish people have run out of patience" over a spate of deadly cross-border attacks by the outlawed Kurdistan Workers' Party (PKK).

But in an interview with the Italian daily La Stampa, Erdogan also said Turkey could call off its threatened incursion if "the Iraq government took urgent and permanent measures against the PKK in Iraqi territory."

Asked what headway Bush had already made in his contacts with Erdogan, White House spokeswoman Dana Perino said the Turks were "appreciative of the support that we are providing in regards of intelligence."

"We are concerned about the challenge posed by the PKK terrorists," she told reporters.

"They should be eradicated, and so we will work with Turkey and the Iraqis to make sure that there is not a safe haven established for the PKK in that region."

With Turkish troops massed along the border with Iraq, Iraqi Prime Minister Nuri al-Maliki on Saturday pledged to clamp down on the Kurdish rebels.

And in Ankara Friday, Secretary of State Condoleezza Rice pledged to "redouble" US efforts to combat the Kurdish rebels, but stressed it would take time and effort to flush them out of their mountainous redoubts.

"It is a difficult problem, rooting out terrorists. This is going to take persistence, commitment," she said.

On Monday, Iraqi Kurdish regional prime minister Nechirvan Barzani proposed four-party talks to resolve the issue of incursions -- with his government as one of the participants.

"This is a transnational issue, complicated by ethnic ties, and no party can find a solution on its own," Barzani wrote in the Washington Post. "To this end, we propose talks among Ankara, Baghdad, Erbil and Washington."

But PKK leader Murat Karayilan called on the Iraqi Kurdish leadership to stand by its ethnic kin.

"No action (against the PKK) can be successful ... as long as we, the Kurds, preserve our unity," he told the Firat news agency, considered to be a mouthpiece of the PKK.

Erdogan was being accompanied by Turkish Foreign Minister Ali Babacan and Defense Minister Vecdi Gonul on his brief visit to Washington, before he heads to Rome for talks with Italian Prime Minister Romano Prodi.

Despite Iraq's announcement of new steps to curb the PKK separatists, Babacan said military options "remain on the table."

Some observers fear that US influence with Turkey has been undermined by a push in Congress to label the Ottoman Empire's World War I massacre of ethnic Armenians as "genocide."

But fierce pressure from both Turkey and the White House appears to have paid off for now, with its Democratic authors agreeing late last month to delay a House debate on the measure.

For his talks with Erdogan, Bush has promised to lay out areas of US cooperation against the PKK including sharing intelligence.

US Defense Secretary Robert Gates said it did not make sense for Turkey to send its forces across the border or to drop bombs "without good intelligence."

Bush will be able to point to one breakthrough executed with Iraqi help, after Baghdad helped secure the release on Sunday of eight Turkish soldiers who had been seized by the PKK in a deadly ambush and held in northern Iraq.