Just off the Mosul road that runs through the vivid green plains of Iraq's Nineveh Province, a Kurdish security officer - a peshmerga - checks our documents, though we are several miles outside Kurdistan Regional Government (KRG) borders. "Careful," he says, gesturing at the road ahead. "There are Arabs."

The checkpoint, manned by Kurdish forces, is on the country's "trigger line", a 300-mile unofficial boundary between the areas run by the KRG and the Iraqi central government - a border that some fear will be the setting for the country's next civil war. The KRG claims that areas of northern Iraq with a large Kurdish population ought to be part of its jurisdiction, and says its peshmergas were invited across the official green line by US forces to help protect the local people. Arab nationalist parties accuse the KRG of occupying disputed land.

The governance of these areas, particularly the oil-rich city of Kirkuk, is a focal point for post-election bargaining over the make-up of the ruling coalition. US forces have begun to play an important role in managing Arab-Kurd tensions, but they are scheduled to withdraw by the end of the year, leaving little time to cut a deal.

In Talkeef, an ethnically mixed town just beyond the checkpoint, trigger-line tensions run high. Bashar al-Kiki, the Kurdish head of the district council, recalls a recent clash between Arab forces, peshmergas and US troops. "I was so scared," he says.

When al-Kiki learned that Atheel al-Nujaifi, the governor of Nineveh, was coming to Talkeef, his heart sank. Under Saddam Hussein, the region's Kurdish minority was excluded from power, but it came to dominate the provincial government after Iraq's 2005 elections, which many Sunni Arabs boycotted. In power, Kurdish parties showed scant regard for bridge-building; in the 2009 provincial elections, Sunnis returned to the polls and al-Hadba, the Arab nationalist party to which al-Nujaifi is affiliated, refused to offer senior posts to anyone from the main Kurdish parties. A boycott movement sprang up, urging officials from Kurdish areas, such as al-Kiki, to cut their links with the provincial government.

So, on the morning that al-Nujaifi appeared in Talkeef, a crowd of demonstrators started to gather. When al-Kiki went to the town gate to explain the sensitivities of the situation, he was faced with five American trucks approaching the checkpoint, plus tanks and helicopters.

“The head of the peshmergas was talking to the Americans, and he received a call from above telling him to let al-Nujaifi go," al-Kiki told me. The armoured vehicles eventually passed through the gate, but were pelted with stones and tomatoes. Later, the governor travelled to another part of the region where a demonstration ended in gunfire and arrests. "I expec­ted bigger consequences," al-Kiki says. "If one peshmerga had decided to stop al-Nujaifi, there would have been a big fight."

Talkeef is surrounded by checkpoints, but the various groups seem to mingle freely within the town. The population consists of Kurds, Christians, Arab Muslims and Yezidis, followers of a pre-Islamic religion whose unusual grooved shrines look like giant lemon-squeezers in the Nineveh landscape. From behind his desk, al-Kiki tackles the problems of a range of constituents, switching between Kurdish and Arabic. In spite of Talkeef's location, security within the town is good, locals say.

Scores of Christian families fleeing a recent campaign of violence in Mosul have sought refuge in Talkeef. "We feel very safe here, protected by the KRG forces and the [Iraqi] police," a Christian leader sitting in the office tells me, adding: "Mainly the KRG." The peshmergas, who patrol the streets, are seen as more effective than the Iraqi security forces.

A political game

An elderly man in a dishdasha and headdress enters the office and is introduced as "the sheikh". Saeed Mohammed Saeed is one of Talkeef's Arab community leaders. "Relations between Kurds and Arabs have always been good, because we have marriage relations," he says. "The situation is not the people, it's the political parties." He is contemptuous of al-Nujaifi's decision to visit Talkeef ("just a political game"), and his take on whether the town should be part of the KRG is diplomatic. "There is a saying that Mosul is the father of poor people. Here there are lots of farmers. The majority feel comfortable if we live with Mosul."

The community members in al-Kiki's office chat and joke with each other, but there are reminders of the wider tensions. Even al-Kiki, who has many Arab relatives, is not always tactful. "In the 1960s there were just Kurds and Yezidis here," he says. "Now there are more Arabs than Christians, unfortunately."

At three o'clock, the visitors have left, and al-Kiki invites us to lunch at the local kebab shop. The streets are calm and almost empty, but an armed soldier accompanies us, and security guards at the office gates spring up nervously to inspect trucks that pass. The strange mix of security and uncertainty that characterises life here lends itself to a pervasive strain of black humour. Having insisted that Talkeef is a stable place, al-Kiki teases me about the town's proximity to Mosul, one of al-Qaeda's last refuges in Iraq. "It is very dangerous," he says in English. He chuckles. "Very dangerous."

This article appeared in this week's New Statesman under the headline "Hair-trigger town"