The withdrawal plan would fulfil one of Obama's central campaign pledges, albeit a little more slowly than he promised. He said he would withdraw troops within 16 months, roughly one brigade a month from the time of his January 20 inauguration.

The officials said they expect Obama to make the announcement this week. They spoke on condition of anonymity because the plan has not been made public.

The US military will leave behind a residual force, between 30,000 and 50,000 troops, to continue advising and training Iraqi security forces, the two officials said. Also staying beyond the 19 months will be intelligence and surveillance specialists and their equipment, including unmanned aircraft, they said.

A further withdrawal will take place before December 2011, the period by which the US agreed with Iraq to remove all American troops.