US marines started to pull out from some positions in the besieged Iraqi city of Falluja early on Friday, witnesses said.
US troops had left many positions in the southern part of Falluja, and had moved back from some others in the western part of the city, according to witnesses.
US forces pounded parts of the city by fighter jets on Thursday with talks for a cease-fire going on.
US marines have been fighting with Iraqi insurgents holed up inthe city for the last three weeks.
Scores of US soldiers and hundreds of rebels were reportedly killed in the conflict in Falluja, a hotbed of uprising against the US-led forces, which began on April 5 with the murder and mutilation of four American contractors there.