The Kurds of northern Iraq have warned that there will be clashes if troops from neighbouring Turkey cross the border.
Ankara is demanding that Turkish forces should enter the north of the country to secure Turkey's interests if the US and Britain go ahead with an attack on Iraq.
Kurdish spokesmen have said that their guerrillas who control the north will oppose any Turkish intervention.
Regional tensions are rising in advance of expected military action by the US and its allies and the atmosphere between two of those allies - the Turks and the Iraqi Kurds - is becoming increasingly embittered.
In the most blunt warning yet, senior officials of the two big Kurdish factions - the Kurdistan Democratic Party (KDP) and its rival, the Patriotic Union of Kurdistan (PUK) - have warned that if Turkish troops cross the border for any reason there will be trouble.
The KDP and PUK have run affairs in an enclave in the north of Iraq since 1991.
The KDP's peshmerga guerrillas control the border regions seen as a possible route for Turkish forces.
KDP spokesman Hoshyar Zebari said: "We will oppose any Turkish military intervention. This is our decision.
Kurdish guerrillas say they will protect their territory
"Nobody should [think] we are bluffing on this issue. This is a very serious matter. Any intervention, under whatever pretext, will lead to clashes."
Mr Zebari said it would be bad for the image of the Americans and British that two of their allies should be "at each other's throats" before the main battle against the Baghdad government had even started.
He also warned that if the Turks intervened, other regional powers such as Iran would also feel free to step in.
As part of the price for their own troops to spring off from Turkey, the Americans are believed to have agreed in principle to the Turkish demand for forces to be involved.
The Turkish foreign minister has said the intervention would be to:
- Head off a potential wave of refugees
- Stop the Iraqi Kurds setting up an independent state
- Prevent Kurdish forces from entering the nearby Iraqi oil cities of Kirkuk and Mosul
The Kurds insist they have no intention of doing any of these things and they say that Turkish intervention would be an unnecessary violation of Iraqi sovereignty.
The Turks are also said to be demanding that Kurdish guerrillas should be disarmed.
The Kurdish spokesmen said they had already agreed that their forces should be dissolved and merged with the Iraqi army and police forces, but not before a democratic federal government has been established in Baghdad.
The Kurds and Turks have been engaged in so far inconclusive talks over Ankara's demands and another meeting is scheduled for Tuesday.