BAGHDAD (Reuters) — The United States is stepping up pressure on Iraq’s prime minister to stop sectarian killers allied to his own government and is stressing its patience is limited for keeping US troops in Iraq to prevent a civil war.Over the past week, several senior US commanders and a top diplomat from the US-led Coalition in Iraq have underlined in background media briefings their support for Nuri al-Maliki’s pledge to disarm the militias loyal to fellow Shi’ite Islamists.

All said they appreciated the delicacy of Maliki’s position and the need to give him time to succeed. But they also voiced mounting frustration at gross corruption and sectarian rivalries within his four-month-old national unity coalition and what they said were continued death squad operations within the police. “We have to give it time,” one senior US military official said. But he added: “We have, wherever we can, to use what pressure, what influence we have to get them as quickly as possible to clear these places out ... There is going to come a time when ... we are going to have to force this issue.”

A senior diplomat said: “It is absolutely essential that Maliki succeeds. Leaders who opted into a government of national unity should behave like a government of national unity.” He added that the patience of the allies to keep troops in Iraq was not endless: “No one wants to leave a country in turmoil and sectarian bloodshed. But it’s not a blank cheque.”

US commanders, like their British counterparts in Shi’ite southern Iraq, are particularly intent on stopping supporters of radical Shi’ite cleric Moqtada al-Sadr, whose backing was crucial to Maliki securing the premiership in April. Though some “rogue elements” of his Iranian-backed Mehdi Army are out of Sadr’s control, they blame the group for much of the bloodshed in Baghdad. But a two-month-old crackdown in the capital has yet to broach their Sadr City stronghold. “The time is short for them to deal with that,” another senior US military official said. “This can’t go on ...”

US commanders say they see no reduction in troop levels before mid-2007. Maliki and worried Sunni minority leaders say troops should stay until Iraqi forces can keep the peace.

President George W. Bush has pledged US support, but the war is increasingly unpopular among American voters, and he has said lately that Maliki, too, has obligations. “Iraq can count on our partnership as long as the new government continues to make the hard decisions necessary,” Bush said a month ago. Some analysts see in that emphasis on Iraqis’ responsibility the groundwork for a change in policy, possibly after November’s congressional elections, and a move to withdraw troops.

US commanders accept that Maliki has his work cut out and that some of the problems with sectarian gangs in the police are the result of the quick-fix US move to bolster security for last year’s elections by drafting militiamen on to the payroll.

“He’s just trying to sort out his own game plan,” a senior US intelligence official said, saying Maliki was trying to get to grips with rival Shi’ite groups in his coalition.

US policy is not to destroy Sadr politically, he said, noting that the young cleric had a popular base and 30 of the 275 seats in parliament, but to “get the militants off the list ... and get Moqtada al-Sadr back in the box”. Officials describe the task of establishing workable government in Iraq as tackling a “Gordian knot”, and some worry that Maliki will fail to impose himself. “In every single ministry ... they’re using that ministry to fill up the coffers of the political parties,” a senior US military official said, describing corruption as a legacy of Saddam Hussein and cautioning that even if the worst is averted, Washington expects Iraq to fall short of an exemplary democracy.

Failure to halt violence could have catastrophic consequences beyond the control of foreign troops and there are concerns among US commanders about how generals from the once dominant Sunni minority in the new, US-trained army would react if they concluded Maliki had given a “free pass” to Shi’ite militias. Unchecked sectarian violence will lead to civil war, the US Middle East commander, General John Abizaid, has said. “I don’t think Americans ... have any idea what will happen in a civil war in this country,” one of the senior US military officials said. “It’s absolutely frightening. That’s given me new impetus to try to see if we can’t turn this thing around.”