"General [George] Casey is assigned the business of making a lot of plans and this is one of the plans that is under consideration," Tony Snow, the White House spokesman, said on Monday.
George W Bush, the US president, discussed the plan with Casey but insisted that any decision would depend on the situation in Iraq.
"In terms of our troop presence there, that decision will be made by General Casey as well as the sovereign government of Iraq based upon conditions on the ground," Bush said. Any recommendation by Casey would be "aimed towards achieving victory".
The New York Times reported on Saturday that Casey had drafted a plan that would reduce the number of US troops in Iraq in September. The number of combat brigades would then be cut from the current level of 14 to five or six by the end of 2007.
Close to 130,000 US troops are currently serving in Iraq.
Democratic Party critics of the president have reacted angrily, saying that the plan appeared to be similar to their calls for a timetable for troop withdrawal which Republicans have called "cutting and running".
Bush is under pressure to bring home at least some US soldiers before the November congressional elections as the Iraq deployment becomes increasing unpopular.
Meanwhile, a Sunni leader in Iraq has said that the armed anti-government campaign will continue until Washington set a timetable for withdrawal of its soldiers.
Tareq al-Hashimi, who is also an Iraqi vice-president, said the prime minister's national reconciliation plan, unveiled on Sunday, failed to offer fighters a reason to stop fighting.
"Leaving the issue of a timetable vague is a way of telling the resistance: 'Continue your fighting to liberate Iraq. They are not going to leave the country'," he said.
Al-Hashimi: The prime minister
will have to talk to the fighters
He said Nuri al-Maliki would have to talk to the fighters and the Baathists if he wants to reconcile Iraq's divided communities.
He agreed that there could be no talks with al-Qaeda but said al-Maliki must talk to "resistance" groups such as the Islamic Army and the 1920 Revolution Brigades, made up of former officers of Saddam Hussein.
Al-Hashimi said al-Maliki's plan also failed to offer details on how he would dismantle Shia militias accused of abducting and killing Sunnis.
"We promised our people that things would improve with the national government but we haven't seen any progress in the security file," he said.
He praised al-Maliki's promise to review laws barring members of Saddam's Baath party from public office and the military, saying the US-sponsored law had worsened sectarian relations. Al-Hashimi said: "We should have a new chapter, a new Iraq for Iraqis."