Nouri al-Maliki on Monday warned Moqtada al-Sadr, a militant Shia cleric, to disband his militia or face being excluded from future Iraqi elections.

The ultimatum from Iraq’s prime minister was the first to single out Mr Sadr’s Mahdi army since a truce was agreed a week ago, and suggests a deepening divide within the country’s Shia community.

“Solving the problem comes in no other way than dissolving the Mahdi army,” Mr Maliki said on Monday in an interview with CNN.

“They no longer have a right to participate in the political process or take part in the upcoming elections unless they end the Mahdi army.”

Mr Maliki initially ordered troops into the southern port city of Basra to tackle so-called criminal elements in the Mahdi army, but the fighting quickly spread across the south and both sides have sued for peace.

Baha al-Aaraji, a senior Sadrist lawmaker, rejected the ultimatum. “The government cannot decide what will happen to the Mahdi army. We are a legitimate force that is resisting the occupation of our country by foreign forces,” he said.

But another senior Sadr aide told Reuters that the cleric would seek rulings from top Shia clerics, including Grand Ayatollah Ali al-Sistani, the most ­senior religious figure in Iraq, on whether to disband the ­militia.

Mr Maliki’s comments come at a delicate time, two days before Mr Sadr’s followers have been called to take to the streets of the capital for a mass anti-US protest, and a day before senior US officials in Baghdad are due to report to Congress on the success of the surge, a reinforcement of US military forces.

General David Petraeus, the US military commander, is expected to recommend a pause in withdrawing troops once an initial cut of 20,000 soldiers is completed in July.

Clashes at the weekend between US forces and the Mahdi army in Sadr city, a slum area in Baghdad and Sadrist stronghold, underscored the dangers posed to the relative peace of recent months. At least 25 people, including five US soldiers, were killed in the fighting.

Mr Maliki’s aggressive stance has won widespread support among other political parties, even as the prospect of a lasting settlement with Mr Sadr recedes.

A cross-party meeting of politicians on Saturday signed a resolution calling for all political parties to ­disband their militias.