Supporters of Shia cleric Moqtada Sadr have staged a mass demonstration in Baghdad in protest against plans to extend the US mandate in Iraq.
An estimated 50,000 protesters chanted slogans such as "Get out occupier!".
Iraqi and US negotiators drafted the deal after months of talks but it still needs approval from Iraq's government.
Under the agreement US troops would withdraw by 2011, and Iraq would have the right to prosecute Americans who commit crimes while off-duty.
The UN mandate for US-led coalition forces expires at the end of this year. About 144,000 of the 152,000 foreign troops deployed there are US military personnel.