American and Iraqi officers in Kirkuk, 240 kilometres (150 miles) north of Baghdad, said the tripartite unit's role and numbers are to be re-evaluated at a high-level meeting on March 9, two days after parliamentary polls.

The US military has repeatedly warned that Arab-Kurd tensions, provoked by disputes over land and oil rights, are the biggest threat to Iraq's long-term stability.

Any break-up or scaling-back of the combined security force would be seen as a major blow to reconciliation efforts.

The force of about 1,350 comprising US troops, Iraqi soldiers and police, and Kurdish peshmerga (former rebel) fighters, aims to build trust between Arabs and Kurds and head off an armed conflict.

Joint patrols began two weeks ago in Kirkuk, an oil-rich, ethnically mixed province, despite objections from Sunni Arabs and Turkmen who say the presence of Kurdish peshmerga is divisive and illegitimate under Iraqi sovereignty.

The force could be increased, maintained or brought to a complete halt.

"The March 9 meeting will give us a better feel for the longevity of the force and then probably how it's tailored," said Lieutenant Colonel Daniel Cormier, commander of the US army's 1st Battalion 30th Infantry Regiment, based at Forward Operating Base Warrior, near Kirkuk city.

"They could grow this force, they could sustain its current levels or they could dismantle it. I think that's all feasible," said Cormier, whose troops are spearheading the joint patrols.

Major General Torhan Yussef, the police chief in Kirkuk city, confirmed the combined security force's role is to be discussed in Baghdad on March 9.

The force -- which was trained by the US military -- was formed in January after months of high-level negotiations between Iraqi, American and Kurdish leaders.

A series of combined security checkpoints have also been set up in Kirkuk and in the provinces of Nineveh and Diyala, all of which contain large tracts of disputed territory.

The autonomous Kurdish regional government, based in the northern city of Arbil, wants its existing three provinces to be expanded into all of oil-rich Kirkuk as well as historically Kurdish-inhabited parts of Nineveh and Diyala.

The central government in Baghdad, however, says Kurdistan's borders should not extend past its existing provinces of Arbil, Sulaimaniyah and Dohuk.

The dispute dates back to post-invasion Iraq in 2003, when Kurdish forces pushed south across the Green Line, a de-facto boundary separating the northern region from the rest of the country, to assert their territorial claims.

Prime Minister Nuri al-Maliki has in the past two years pushed Iraqi troops north to bolster their presence in the disputed areas.

The result has left troops from Iraq's mostly Arab army facing off against Kurdish peshmerga along the so-called "trigger line" that stretches across Iraq for about 650 kilometres between the Iranian and Syrian borders.

They have clashed on several occasions.

US forces have said the lack of cooperation between Iraqi and Kurdish forces has also created a security vacuum which has been seized on by insurgents to launch attacks against civilian minorities in the disputed areas.

General Ray Odierno, the top US officer in Iraq, has warned Kirkuk is a major problem that must be tackled by the country's next government.

"We keep pushing off the issue of Kirkuk, keep pushing off the disputed areas. It's going to have to be dealt with," Odierno told reporters in Baghdad last month.

The issue is especially pressing for the US military as American combat troops are due to withdraw from Iraq in August, precluding their involvement in frontline operations after that date.

In Kirkuk, mid-ranking US officers told AFP they would be disappointed if the force was scrapped after the considerable efforts made to put it together.

Cormier, however, who served in the Sunni bastion of Fallujah and the capital Baghdad during previous tours of Iraq in 2003 and 2005, said the decision was not in military hands.

"We follow orders and we do what we're told so I sympathise, but at the same time it's not our decision," he said.

"It is a political decision. From a security standpoint the force has been very good. We are doing what we can to try and defuse the ethnic tensions in the area while we still can."