WASHINGTON (AFP) - President George W. Bush on Monday faces crisis talks with Turkish Prime Minister Recep Tayyip Erdogan as he vies to dissuade his "war on terror" ally from an incursion into Iraq to hunt down Kurdish rebels.

Ahead of the meeting at the White House, Erdogan warned that Turkey's patience over cross-border attacks by the outlawed Kurdistan Workers' Party (PKK) was running out.

But the Bush administration, while promising US support against the PKK, is keeping up the pressure for Turkish restraint for fear of destabilizing one of the few calm zones of Iraq.

And 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.

In Ankara Friday, Secretary of State Condoleezza Rice pledged to "redouble" US efforts to combat the Kurdish rebels attacking Turkey from northern Iraq, while warning against unilateral military action.

Rice acknowledged that the United States had an "obligation" to help Ankara -- a close NATO ally -- but stressed it would take time and effort to flush out the rebels.

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

But for Erdogan, facing public outrage over a spate of deadly attacks by PKK guerrillas, time is running out.

"Our visit comes at a time when (Turkish-US) relations are undergoing a serious test," Erdogan told reporters before flying out of Istanbul on Saturday.

"We have run out of patience with the terrorist attacks being staged from northern Iraq," he said, adding that he hoped his meeting with Bush would produce "concrete measures."

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."

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

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."

Turkey has warned that it could restrict US access to the Incirlik airbase, a crucial staging post for US supplies bound for Iraq and Afghanistan, if the genocide resolution passes the full House of Representatives.

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.

"We will have a good, substantive discussion, as you would expect allies to do. And I'm looking forward to seeing him here in the Oval Office," Bush told reporters last week.

US Defense Secretary Robert Gates said it did not make sense for the Turks to send its forces across the border or dropping 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.

"We applaud the efforts of the government of Iraq to secure the release of the hostages," State Department spokesman Sean McCormack said in a statement while accompanying Rice on a visit to Jerusalem Sunday.