A modest drawdown of United States forces from Iraq could start within weeks but troop numbers will remain close to their current level for at least a year, the top US commander in Iraq has told Congress.
Gen David Petraeus said that force levels could return by next August to about 130,000, the number that were in Iraq before this year's "surge" that deployed an extra 30,000.
In testimony before the House armed services and foreign affairs committees that was interrupted by anti-war protesters a number of times, the general said the counter-insurgency strategy adopted earlier this year was working but said it was too early to consider reducing the scope of the US military mission.
"I believe that we will be able to reduce our forces to the pre-surge level of brigade combat teams by next summer without jeopardising the security gains that we have fought so hard to achieve.
"Beyond that, while noting that the situation in Iraq remains complex, difficult and sometimes downright frustrating, I also believe that it is possible to achieve our objectives in Iraq over time, although doing so will be neither quick nor easy," Gen Petraeus said.
The general's testimony came as President George Bush prepares to deliver his own report on the surge and to address the nation on Thursday in defence of his strategy in Iraq.
Most Americans, according to opinion polls, and a majority in Congress oppose the surge and want an early withdrawal of most US forces but Gen Paetraeus's call for the maintenance of high troop levels well into next year will help the president to resist calls for a change of course.
Gen Petraeus said that a unit of about 2,000 Marines will leave Iraq later this month, followed in December by an army brigade numbering 3,500 to 4,000 soldiers. Another four brigades would be withdrawn by the middle of July 2008 and a decision about further reductions would be made next March.
Using charts to illustrate a drop in sectarian violence and a dramatic improvement in security in some parts of Iraq, the general acknowledged that military success has not been accompanied by political progress.
"Lack of adequate governmental capacity, lingering sectarian mistrust, and various forms of corruption add to Iraq's challenges," he said.
The US ambassador to Iraq, Ryan Crocker, said that, despite formidable political and challenges, it remained possible to create a stable, democratic Iraq at peace with its neighbours.
"The cumulative trajectory of political, economic and diplomatic developments in Iraq is upwards, although the slope of that line is not steep.
" The process will not be quick, it will be uneven, punctuated by setbacks as well as achievements, and it will require substantial US resolve and commitment.
"There will be no single moment at which we can claim victory; any turning point will likely only be recognised in retrospect," he said.
At the start of yesterday's hearing, the Democratic chairman of the House armed services committee, Ike Skelton, called upon Gen Petraeus and Mr Crocker to justify continued US commitment to Iraq despite the Iraqi government's lack of political progress.
"Why should we continue sending our young men and women to fight and die if the Iraqis won't make the tough sacrifices leading to reconciliation? Every promising development so far has not turned out to be the solution for which we had hoped," he said.
House foreign affairs committee chairman Tom Lantos dismissed the proposed reduction in troops as "a token withdrawal", provoking a sharp rebuttal from Gen Petraeus.
"A very substantial withdrawal," the general said.
Earlier, Gen Petraeus appeared to respond to a full page ad in the New York Times by the anti-war group MoveOn.org, which dubbed him General Betray Us and accused him of "cooking the books" on Iraq on behalf of the white House.
"Although I have briefed my assessment and recommendations to my chain of command, I wrote this testimony myself.
" It has not been cleared by nor shared with anyone in the Pentagon, the White House or the Congress until it was just handed out," the general said.