U.S. Special Forces troops are working with Kurdish military units with the aim of penetrating Iraqi-held territory once an American invasion begins, spotting targets for U.S. airstrikes and laying the groundwork for seizing Kirkuk, a strategic oil city in northern Iraq, Kurdish officials say.

The deployment marks the first known instance of American forces blending with Kurdish units, which are based in a haven beyond the control of Iraqi President Saddam Hussein's government. Several dozen U.S. troops are already stationed in the Kurdish zones, largely invisible to the public, the officials say. More will begin arriving in the next few days, one Kurdish official said. The precise identity of the U.S. forces could not be determined.

In interviews with several Kurdish officials over the past few weeks, the outlines of cooperation with the U.S. forces have become clear, despite repeated public assertions that armed Kurdish forces were meant to confine themselves to the autonomous zone. Kurdish officials have long expressed their desire for a military link with the Americans.

The joint work is taking place both in the zone ruled by the Kurdistan Democratic Party, or KDP, and with its sometime rival, the Patriotic Union of Kurdistan, Kurdish officials said. Planning began a year ago, one Kurdish official said.

"We are willing to cooperate with anyone who is going to bring democracy to Iraq," said Masrur Barzani, who heads the KDP's intelligence department.

The Special Forces troops have joined Kurdish units that will lead them into areas around Kirkuk that were once populated largely by Kurds, the officials said. "That is what is happening," said a high-ranking Kurdish military official. The Iraqi government has driven tens of thousands of Kurdish civilians from the region over the years.

The Kurds lack the technology to call in U.S. airstrikes, Kurdish officials said. "The Americans have the technology and the training. We have the numbers and the morale, and we know the area," said Azad Miran, chief of KDP military operations. "Spotting is vital. It has to happen."

Kurdish leaders have pledged to the United States to keep their forces from entering Kirkuk, a city of 1 million residents -- about half of them Kurds -- 150 miles north of Baghdad. "It is in our interest to coordinate with our friends," Barzani said.

A Kurdish move into Kirkuk would upset Turkey, which fears that the growth of Kurdish influence in post-Hussein Iraq would reawaken nationalist aspirations among its own large Kurdish minority.

The Iraqi Kurds are seeking to cement the autonomy they have had since a failed uprising against Baghdad a dozen years ago. After Iraqi forces put down the revolt, the United States and Britain guaranteed the security of a broad swath of northern Iraq by patrolling the skies with fighter jets. The Turks also claim Kirkuk on historical grounds and have threatened to occupy it themselves if Kurdish forces move in.

U.S.-Kurdish cooperation is going ahead despite Turkey's reluctance to reach agreement with Washington over joining the anti-Hussein drive. Talks among Turkish officials, Kurdish representatives and U.S. special envoy Zalmay Khalilzad are scheduled to get underway in Ankara on Monday. The Bush administration had planned to send 60,000 troops into northern Iraq, but Turkey has withheld permission for the troops to pass through its territory.

If Turkey intervenes in northern Iraq, Kurdish cooperation with the United States will be disrupted, say the Kurds, who have threatened to take up arms against the Turks. "Having Turkish troops in Kurdistan means war. It would be a major war," KDP leader Massoud Barzani predicted in an interview.

War fever has begun to grip the 31/2 million Kurds in the north. The economic situation in the Kurdish region is dire, and the prolonged advance toward war has dried up commerce. The city of Irbil shelters 100,000 Kurdish refugees from the Kirkuk area, and they are eager to go home.

Kurdish military forces, known as pesh merga, or "those who face death," have been mustered at bases throughout the region. KDP forces plan to occupy towns and villages in a large arc from a point near Mosul in the north to areas south of Kirkuk that were once home to Kurdish civilians. Patriotic Union of Kurdistan troops would move from the eastern side of the Kurdish autonomous zone. Pesh merga commanders expect U.S. air power to destroy fixed Iraqi positions and artillery that could threaten Kurdish towns in the zone.

Commanders predict that Arab settlers brought to the region by the Hussein government will flee if war breaks out. The pesh merga will not enter traditionally Arab villages, and it is unclear who will take Arab towns near Mosul.

Iraqi troops in Mosul and Kirkuk are under the command of Izzat Ibrahim Douri, vice chairman of the Revolutionary Command Council and one of Hussein's top deputies. He led Iraqi troops that put down the 1991 uprising in Kirkuk. Kurdish officials predicted that Iraqi forces defending the countryside and outskirts of both cities would fold quickly. The areas south of the frontier between Kurdish and Iraqi territory are manned by regular Iraqi troops from the First and Fifth Army Corps. A mechanized and armored Iraqi Republican Guard division has withdrawn from Mosul, officials say. Another Republican Guard division remains in Kirkuk, but one Kurdish official said he expected that unit to withdraw toward Baghdad if bombs begin to fall.

"The Iraqis will try to draw the Americans deep into Iraq and inflict casualties," the official said.

If Turkey maintains its refusal to let U.S. forces enter northern Iraq from its territory, the bulk of Americans assaulting Kirkuk would come from western Iraq, the Kurds say. Kurdish officials have also predicted that clandestine Kurdish forces in Kirkuk would revolt, complicating the Iraqi defense.

Kurdish military volunteers known as pesh merga trained last week at a Kurdistan Democratic Party base in Irbil, 150 miles north of Baghdad.