MOSUL, Iraq - U.S. officials are hoping joint patrols between Iraq's largely Arab army and Kurdish troops will build trust in tense disputed northern areas, dampening the tinder that many fear could ignite Iraq's next war.

The troops themselves aren't so sure.

We don't need the Iraqi army here, said Kurdish Peshmerga soldier Shamok Haydi, 28, from his checkpoint outside the small, mountain-ringed town of Wana, which sits on the western outskirts of Iraq's most violent city, Mosul.

They will cause problems and people won't accept them.

Six and a half years after the U.S.-led invasion removed Saddam Hussein, northern Iraq is at the heart of a struggle between minority Kurds and Baghdad's Shi'ite Arab rulers over control of its territory and the vast lakes of oil underneath.

The Kurds claim many parts of northern Iraq, including the oil-producing city of Kirkuk, as their ancient homeland and want to incorporate them into their peaceful enclave, which has been largely autonomous with Western backing since 1991.

U.S. officials, who are racing to pacify Iraq before U.S. combat troops pull out by September next year, see the row as the greatest threat to the country's stability as the Sunni-Shi'ite violence which nearly tore it apart fades.

Saddam's displaced thousands of Kurds from Kirkuk and other areas in a policy of Arabisation, but Arab residents say Kurds have moved in aggressively after 2003 to tip the balance the other way.

A referendum on the status of the disputed territories has been delayed and U.N. officials fear it could spark a civil war.

Thus far, there have been several standoffs between Arab and Kurdish troops in contested zones, but no actual armed conflict.

SECURITY, NOT POLITICS

In August, the commander of U.S. forces in Iraq, General Ray Odierno, suggested staffing checkpoints and patrols with tripartite forces from Iraqi Army, Peshmerga and U.S. troops.

The idea is simple enough: by working together and building relationships, they'll be less likely to shoot at each other.

Odierno envisages the U.S. military as akin to peacekeepers in an increasingly stable but still combustible region.

Iraqi and U.S. officials say commanders on all sides agree in principle but not yet on the details. Some Arab politicians in disputed areas strongly oppose it. Odierno told reporters in Washington this week: we still have some ways to go.

Like many towns in this volatile part of Iraq, Wana has a mixed population of ethnic Kurds and Arabs. Though disputed, it is de facto controlled by Peshmergas tied to Iraq's Kurdistan region, mostly autonomous with Western backing since 1991.

The yellow sun of the Kurdistan flag flies from buildings and checkpoints, often near images of President Masoud Barzani. Iraq's black, white and green flag is nowhere to be seen.

Yet follow the Tigris downstream toward Mosul and Peshmerga checkpoints give way to those of the largely Arab Iraqi army. There, Arab soldiers raise similar concerns about Kurds.

Ask any families around here, they'll say the same thing: they don't want the Peshmerga here, said specialist Mehdi Naim, manning a checkpoint in a largely Arab neighborhood of Mosul.

I don't think it's a good idea, even with the Iraqi army alongside, he said. Some of Mosul's Arab residents have complained of abuse from Kurdish troops since 2003.

Such remarks raise the question of whether the patrols, however well intentioned, may inflame rather than cool tensions.

But with al Qaeda and other groups still active around Mosul, targeting local forces and civilians in an attempt to foment ethnic conflict in north Iraq, cooperation is urgent.

A series of huge bombings last month in disputed parts of Nineveh triggered accusations of blame between Arabs and Kurds, escalating a dispute that plays into the hands of insurgents.

This is about security, it's not about politics, Colonel Gary Volesky, commander of U.S. forces in Mosul, told Reuters.

What the insurgency has done in some of these areas is: there's a gap. You've got a checkpoint in the north, one in the south and a gap insurgents can move through uncontested, where these attacks have occurred. We're shutting down those gaps.

NO RESPECT
Perhaps predictably, Arab residents of Kurdish controlled areas and Kurd residents of Iraqi Army zones seem the most keen on joint forces: each complains of discrimination by the other.

We are persecuted by the Peshmerga, said Mahmoud Ahmed, an Arab employee of Mosul dam who said he is often late because of Peshmerga road blocks. They have no respect for Arabs at all.

Kurdish and Iraqi troops came close to a shootout over the eastern town of Khanaqin in August last year. In Nineveh this year, U.S. forces have had to intervene as mediators three times to prevent conflict between heavily armed troops on each side.

In one standoff, Iraqi Prime Minister Nuri al-Maliki ordered troops to Mosul dam after hearing of a security threat there, raising tensions with the Peshmergas who control the dam.

In another, Nineveh governor Atheel al-Nujaifi, who is embroiled in his own dispute with Kurds, was stopped on a road by Peshmergas wielding machine guns and grenade launchers. Well armed Iraqi troops showed up, but the situation was defused.

The broker role U.S. troops have played in dousing these tensions has raised fears about what may happen when they leave.

If the Americans go, we're sure there'll be a civil war, said Ahmed Ali, an Arab in a Kurdish controlled part of Nineveh, as he glanced nervously at the Peshmergas keeping an eye on him.

(Additional reporting by Aseel Kami in Baghdad; Editing by Samia Nakhoul)

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