Kurdish leaders yesterday accused Turkey of delaying the long-awaited northern offensive by US forces to topple Saddam Hussein.

"The Americans are so frustrated with the Turks it is unbelievable," said Hoshyar Zebari, a Kurdish leader, yesterday after talks with American and Turkish officials in Ankara.

In one incident the US was particularly angered when its strike aircraft were unable to give prompt support to a combined unit of US special forces and peshmerga (Kurdish soldiers) involved in a firefight with the Iraqi army, according to sources in Washington.

Turkey has refused to bow to demands from the US, Britain and Germany that it not invade Iraq in an effort to reduce the influence of the Iraqi Kurds in any post-Saddam settlement. Germany yesterday threatened to withdraw its early-warning Awacs planes protecting Turkish airspace if the Turks carry out a threat to join the war in northern Iraq.

Overnight reports that 1,500 Turkish troops had crossed the border into Iraqi Kurdistan were denied by Mr Zebari and the Turkish foreign ministry.

Also yesterday, US commander Tommy Franks said that the American forces fired five missiles against Islamic militants based in the eastern mountains of northern Iraq linked to al-Qa'ida. Kurdish sources said 100 people were killed in the attack by Tomahawk missiles overnight Friday.

The Kurds have now put their forces under the command of the US-led coalition in an effort to make themselves a more valuable partner of the US than Turkey in the war. They have also made available four airstrips for US forces to enter Iraqi Kurdistan as a base from which to advance on the northern cities of Mosul and Kirkuk.

The explosion of bombs or missiles illuminated the night sky over Mosul and Kirkuk where the First and Fifth Iraqi Army Corps, each with five divisions, are dug in. The Khalid military camp, one of the largest in Iraq, and the secret police headquarters in Kirkuk were hit, according to Mr Zebari.

The Kurdish forces would like to paint themselves as full military allies of the US, especially as they have a somewhat different agenda, including the return of 300,000 Kurdish refugees to Kirkuk and Mosul provinces.

Turkey has threatened to send its army across the border if either city is taken by the Kurds.

The US has abandoned its plans for an American military government of Iraq after the expected fall of President Saddam, said Mr Zebari after talks with US officials. Instead there would be an Iraqi interim authority which would include the Iraqi opposition and others not connected with the present government.

American military assets on the ground in northern Iraq are not large. There are peshmerga units combined with a small number of US special forces. The US could also fly in airborne brigades, but could not mount anything like the heavy armoured attack being made on the Iraqi army in the south of the country. If it did rely heavily on the Kurds then this might precipitate the Turkish intervention which the US has been trying to avoid.

Mr Zebari said there had been one skirmish in which a US/peshmerga unit had called in an air strike that killed three Iraqi soldiers. He hinted that a general attack might occur in two or three days, but the frontline remained quiet yesterday.