The Bush administration and military leaders are sounding optimistic notes about scaling back U.S. troops in Iraq next year, as public opposition to the war and congressional demands for withdrawal get louder.

Contingency plans for a phased withdrawal include proposals to further postpone or cancel the deployment of a Fort Riley, Kan., brigade and an option to put a combat brigade in nearby Kuwait in case it is needed, said a senior Pentagon official.

While military leaders would not confirm the size of possible withdrawals, conversations with defense officials and analysts suggest troop levels could drop below 100,000 next year, contingent on the progress of the Iraqi government and its security forces. There are currently about 155,000 U.S. troops in Iraq.

The official, who asked not to be identified because plans are not final, said stresses on the National Guard and Reserves are also factors.

On Wednesday, Pentagon officials would not confirm any reduction plans. Defense Department spokesman Bryan Whitman said there has been "very positive" development of Iraqi security forces, and he added that "we plan for every possible contingency," including a smaller coalition force.

President Bush has refused to set a withdrawal timetable, and the administration has consistently said U.S. troops will remain as long as needed. Led by Vice President Dick Cheney, the administration has strongly opposed last week's call by Rep. John Murtha, D-Pa., for a U.S. withdrawal within six months.

Public support for the war has fallen in recent weeks, fed by events such as the 2,000th U.S. military death there and allegations of the secret imprisonment and torture of some Iraqi prisoners by the Iraqi government.

In recent days, some administration and military officials have made positive-sounding comments about a possible withdrawal.

Lt. Gen. John Vines, chief of the Multi-National Corps-Iraq, said Iraqi security forces — which number about 212,000 now — are making excellent progress, an oft-cited precondition for removing U.S. troops. He said 36 Iraqi battalions are responsible for their own areas of operation.

Secretary of State Condoleezza Rice told FOX News on Tuesday that the U.S. would probably not need to maintain its current troop levels in Iraq "very much longer." Defense Secretary Donald H. Rumsfeld told radio talk show host Sean Hannity that the war would wind down over the next two years, and "we'll see the coalition forces being able to pare down and pass over responsibility to Iraqi Security Forces on an orderly basis" after the Dec. 15 elections.

The Washington Post, quoting anonymous sources, reported Wednesday that the Pentagon tentatively plans to reduce the number of U.S. forces in Iraq early next year by up to three of the 18 combat brigades.

"With the number of units available, they are coming to the point where they simply were not going to have enough brigades," said Dan Goure, a military analyst with the nonpartisan Lexington Institute, which studies public policy. "There is a recognition that the number has to come down because of the stress that was being placed on the force."

Goure added, "There is a plan that has been in the works for at least six months with the idea that we possibly could reduce the number of troops."

Rumsfeld and others have said they expect U.S. forces to drop back down to the base level of about 138,000 after the Dec. 15 election for Iraq's new government. So far, the Pentagon has identified 92,000 troops who will be rotated into Iraq through mid-2008, though Rumsfeld has cautioned that should not be taken as a final number.

Officials have put off the deployment of the 1st Brigade, 1st Infantry Division, based at Fort Riley, Kan., which was originally scheduled to deploy before the election. That deployment has not yet been scheduled.

The troops currently in Iraq comprise 17 brigades and three additional battalions — which add up to about another brigade. The three battalions are scheduled to return home after the first of the year. A brigade normally numbers between 3,500 and 5,000 soldiers, while battalions average about 800.

Basing a brigade in Kuwait, where it could train and be ready for any emergency action, would not be an unexpected move. That country has long been used as a staging area for troops entering and leaving Iraq.