The rival US presidential hopefuls have aired bitter disagreements over the Iraq troop surge as they put questions to American military commander General David Petraeus.
Democrats Hillary Clinton and Barack Obama say they would end America’s military involvement within the first year or two of their presidency, should they win.
But Republican John McCain, a former Vietnam prisoner of war, said he believed US forces were succeeding and it would be irresponsible to pull out before the Iraqi government and security forces could stand on their own.
“I do not want to keep our troops in Iraq a minute longer than necessary to secure our interests there,” he said.
“Our goal, my goal, is for an Iraq that no longer needs American troops.
“But I also believe that the promise of withdrawal of our forces, regardless of the consequences, would constitute a failure of political and moral leadership.”
Democrat Hillary Clinton said she “fundamentally disagreed” with McCain’s view.
“Rather, I think it could be fair to say it might well be irresponsible to continue the policy that has not produced the results that have been promised time and time again,” she said.
The former first lady also raised the cost of the war and the issue of the withdrawal of British troops from Basra.
Meanwhile, Clinton’s rival Democrat candidate Barack Obama called for a “diplomatic surge” including talks with Iran, to help stabilize the situation in Iraq.
General Petraeus warned that pulling troops out of Iraq too quickly would jeopardize the “fragile” security gains made in recent months.
He said the “surge” in US troop numbers had resulted in a “significant but uneven” improvement in the security situation across the country.
Testifying before the Senate, he warned al Qaeda could “still stage a resurgence”.
The general said troop levels would be reduced to the levels before the “surge”, at which point there would be a 45-day review period.
This would be used to work out how many troops would be needed in the future.
The war in Iraq is seen as a key issue in the forthcoming presidential election in November.
The American death toll in Iraq has passed 4,000 as the conflict stretches into its sixth year and recent figures confirm a reversal of a trend of gradually decreasing violence.