The Pentagon has approved a request by the new US commander in Iraq for an extra 2,200 military police.
The police are to help deal with an anticipated increase in detainees during the Baghdad security crackdown.
US Defence Secretary Robert Gates said the request for extra MPs is in addition to the 21,500 combat troops that President Bush is sending for the Baghdad security plan, along with 2,400 support troops.
Mr Gates said there were early indications that the Iraqi government is meeting the commitments it made to bolster security, although he warned it was too early to reach any firm conclusions about the outcome.
Gordon England, the deputy defence secretary, told Congress this week that the number of required support troops could reach 7,000.
The day-to-day commander of US troops in Iraq, Lt Gen Raymond Odierno, has recommended that the higher troop level be maintained until February 2008, the New York Timesreported.
House Democratic leaders intend to propose legislation requiring the withdrawal of US combat troops from Iraq by the fall of 2008, and even earlier if the Iraqi government fails to meet security and other goals, Democratic officials said.