BAGHDAD: An agreement aimed at ending fighting in the Baghdad bastion of Iraqi Shi'ite cleric Moqtada Al Sadr appeared on the verge of collapse yesterday after gunmen attacked US troops.

The deal between the ruling Shi'ite alliance and Sadr's opposition movement in parliament to end fighting in the Sadr City slum district was formally signed on Monday.

But with the ink barely dry on the 16-point pact, clashes flared overnight and through yesterday, raising questions over how much control the anti-American cleric has over some of the Mehdi Army militiamen who profess allegiance to him.

A Mehdi Army statement read out in mosques in Sadr City said the deal must be respected.

Nevertheless, the US military said violence broke out between its troops and militants in Sadr City. TV footage showed five children running for cover as automatic gun fire .

Iraqi police said at least 11 people had been killed and 20 wounded in clashes.

US troops were attacked numerous times with small arms fire.

A senior political aide to Sadr urged patience with the truce, saying it might take time to filter down.

"Ceasefires cannot always be implemented immediately. Violations will happen in the first few days. Some armed groups may not be aware of it," Luwaa Sumaisem said.

Militants slammed four mortar rounds into the Iraqi interior and justice ministries in central Baghdad but there were no casualties, security officials said.

Three mortar rounds struck the interior ministry building and one hit the justice ministry, they said, adding that the operations room of the interior ministry was damaged in the attack.

There was no immediate word on who was responsible although US and Iraqi government forces have been clashing with Shi'ite militiamen since late March.

Meanwhile, the US military must concentrate on the war in Iraq despite concerns about the stress on the force and its readiness for future wars, Defense Secretary Robert Gates said.

"Morale is high, as is recruiting and retention - particularly among units either in or just returning from Iraq and Afghanistan," Gates said. As for the possibility of stretched US forces being confronted with a war elsewhere, Gates said: "There is a risk, but it is a prudent and manageable one."