A deal aimed at ending fighting in the Baghdad bastion of Iraqi Shi'ite cleric Moqtada al-Sadr was on the verge of collapse on Tuesday after gunmen launched a spate of attacks on US troops.
The agreement between the ruling Shi'ite alliance and Sadr's opposition movement in parliament to end fighting in the Sadr City slum was formally signed on Monday.
But with the ink barely dry on the 16-point pact, clashes flared overnight, raising questions over how much control the anti-American cleric has over some of the tens of thousands of gunmen who profess allegiance to him.
The US military said fighting flared between its troops and militants in Sadr City overnight, where seven weeks of clashes have already killed hundreds of people.
Iraqi police said 11 people were killed and 20 wounded in clashes in the eastern Baghdad district.
They did not give precise details but the US military said it had killed at least three militiamen trying to plant roadside bombs. US troops came under attack numerous times with small arms fire, the military said.
A spokesman for the US military in Baghdad, Lieutenant-Colonel Steven Stover, said US forces only targeted militants launching attacks.
"We're not looking for a fight -- we are establishing a safe neighbourhood for Sadr City residents," Stover said. "They (the militants) are obviously not listening to any agreement."