Rice deferred to the decisions of President Bush and military commanders as Republicans and Democrats on the Senate Foreign Relations Committee pressed her for more specifics on the U.S. strategy in Iraq.
Asked specifically whether the United States would have troops in Iraq in five or 10 years, Rice said: "I think that even to try and speculate on how many years from now there will be a certain number of American forces is not appropriate."
At the White House, spokesman Scott McClellan also would not rule out the possibility of a U.S. troop presence that far in the future.
"In terms of decisions about troop levels, we've always said that we will look to our commanders on the ground and they will be the ones who will make decisions based on circumstances on the ground," McClellan said.
Lawmakers also pressed her on strategy for dealing with Iran and Syria. U.S. officials have accused Syria of allowing foreign fighters to flow across its borders into Iraq and Iran of supporting the insurgency.
Rice said the United States was using diplomatic means to urge a change in the behavior of both countries — but she stopped short of ruling out military force. "I'm not going to get into what the president's options might be," Rice said. "I don't think the president ever takes any of his options off the table concerning anything to do with military force."
Testifying before the committee for the first time since February, Rice sought to reassure jittery members of Congress that the Bush administration had a plan for success: helping Iraqis clear out insurgents and build durable, national institutions.
She told lawmakers the United States will follow a model that was successful in Afghanistan. Starting next month, she said, joint diplomatic-military groups — Provincial Reconstruction Teams — will work alongside Iraqis as they train police, set up courts, and help local governments establish essential services.
But even as Rice tried to crystallize the plan, Republicans and Democrats asked her pointed questions they say Americans need to know.
"I'm not looking for a date to get out of Iraq," Sen. Joseph Biden, the top Democrat on the panel, said. "But at what point, assuming the strategy works, do you think we'll be able to see some sign of bringing some American forces home?"