A new pact that faces final approval from parliament will keep US troops in Iraq for up to three more years. By June 2009 US forces will pull back to major bases.
Iraq's Shiite-led government has begun taking control of the anti-insurgent Sunni fighters who have helped improve security across the country.
A rare daytime US airstrike in Sadr City on Thursday came as residents said that soldiers were warning them to leave parts of the district, which is a bastion of support for the anti-American cleric Moqtada al-Sadr.
Moqtada al-Sadr's Mahdi Army fought US, Iraqi forces in Baghdad and Basra on Tuesday.