Echoing previous statements from military commanders, the US secretary of state said on Sunday: "I think it's entirely probable that we will see a significant drawdown of American forces over the next year. It's all dependent on events on the ground."
Last week, Donald Rumsfeld, the US defence secretary, declined to predict exactly when the US forces would be out of Iraq.
"The level of the forces in Iraq will depend on conditions on the ground and the recommendations of the commanders," he said to reporters at the Pentagon.
He said he had not received a recommendation from General George Casey, the top commander in Iraq, on whether or when to reduce the size of the force.
George Bush, the US president, has said that decision will be up to a future US president and a future Iraqi government.
There are about 133,000 American troops in Iraq, but military officials have expressed hope they can reduce that to below 100,000 by end of the year.
Rice, appearing on NBC television, pointed out that Casey "has talked about a significant reduction of American forces over the next year. And that significant reduction is because Iraqi forces are taking and holding territory now."
The military is carrying out plans announced by Rumsfeld in December to cut troop levels this year by up to 7,000 soldiers by cancelling the planned deployment of two Army brigades.
Further cuts are being debated.