U.S. and Turkish officials say that the United States needs to step up efforts to prevent Kurdish separatists from operating cross border attacks on Turkey from Iraq.

The issue has taken on greater urgency as Kurdish guerrillas have escalated attacks in Turkey and provoked Turkish threats to launch a military incursion into Iraq, a move that could have serious implications for the U.S. efforts to stabilize Iraq.

U.S. officials say they consider the separatist Kurdistan Workers' Party or PKK to be a terrorist organization and are working closely with Turkey to combat the threat. But officials have had few examples of success against the PKK to point to.

Responding to criticism of U.S. inaction from Turkey, U.S. Brig. Gen. Perry Wiggins, deputy director of operations for the Joint Chiefs of Staff suggested that the United States was focused on its own mission in Iraq.

"We continue to work with Turkey," Wiggins said. "Our military's focus is on Iraq and the situation in Iraq."

He added: "As the secretary of defense has said, any disruption up in Northern Iraq would not be helpful at this time."

The comment came a week after Turkey's military chief, Gen. Yasar Buyukanit asked the government to set political guidelines for an incursion into northern Iraq. The Turkish military has said that an incursion may be necessary because the U.S. and the Iraqi governments have failed to stop attacks across the border.

The issue is highly sensitive in Turkey, which has been battling the PKK since 1984 in a conflict that has killed tens of thousands of people. Tension over whether the Turkish military will take action in Iraq has intensified as the country approaches an election later this month.

The PKK has escalated attacks this year, killing at least 67 soldiers so far. More than 110 rebels were killed in the same period.

During the 1990s, Turkish troops penetrated Iraqi territory several times, sometimes with as many as 50,000 troops. The Turkish forces withdrew, leaving behind about 2,000 soldiers to monitor rebel activities.

Buyakanit complained to senior White House officials including Vice President Dick Cheney during a U.S. visit in February and Turkish officials have continued to press the case in Washington.

"Clearly our expectations are not being met," said a Turkish diplomat in Washington, who requested anonymity because he was not authorized to speak on the record. "We are using every channel to express our unhappiness about what is not happening."

Meanwhile, Turkey, a key NATO ally continues to provide vital support to U.S. operations in Afghanistan and Iraq through Incirlik Air Base in southern Turkey, one of the most important U.S. military assets in the region.

Privately, some U.S. officials are raising concern that the United States has not moved aggressively to allay Turkish concerns. They say that U.S. policy makers are underestimating the risk that Turkey's pursuit of the PKK in Iraq could lead to a wider conflict with the Kurdish forces which are a key part of the Iraqi army.

One senior U.S. diplomatic official says that the likelihood of Turkey invading Northern Iraq ahead of the July 22 Turkish elections is very high.

The official, who requested anonymity because of the sensitivity of the issue, said that the U.S. government has not focused sufficient attention or resources to address Turkish concerns.

"I think we ought to be doing everything we can to counter the PKK," the official said. "The biggest problem is getting the U.S. to do what it should do."

The official added that inaction by the U.S. risks alienating Turkey.

"I think that 70 million Turks are important," the official said.

Capturing PKK fighters in Iraq might mollify the forces in Turkey in favor of an invasion, the official said.

Some analysts believe that the United States is too distracted by its efforts to stabilize Iraq and fight insurgents to focus on the PKK. A move against the PKK would require shifting military resources to northern Iraq, a region that has been relatively calm from Washington's perspective.

"Arresting PKK members in northern Iraq is not so easy," said Mark Parris, a former U.S. ambassador to Turkey now a visiting fellow at The Brookings Institution. "A lot of crockery can be broken in that part of the world."

Analysts say that the United States has also been reluctant to pressure Kurdish politicians in Iraq-- who Washington considers reliable allies in a chaotic political atmosphere -- to crack down on the PKK.

"A Turkish military operation is a disaster waiting to happen," said Bulent Aliriza, a Turkish scholar at the Washington-based Center for Strategic and International Studies. "But the United States has not been able to reconcile an important tactical relationship with the Kurds in Iraq with the long-standing strategic alliance with Turkey."