The debate over the timing for bringing U.S. troops home from Iraq resumed on Sunday with Defense Secretary Donald Rumsfeld saying it may be possible to reduce the number of U.S. troops there from nearly 160,000 to fewer than 100,000 by the end of next year.

But Rumsfeld rejected the notion of setting a date by which the United States will leave Iraq altogether.

"Ask yourself if that country, with their oil and their water and their intelligent people, is turned into a haven for terrorists, compared to the opportunity we have to have that be a democratic system that's respectful of its people, at peace with its neighbors, and the difference for us — the dangers for the American people will be vastly different depending on how we manage ourselves," Rumsfeld said.

"Put yourself in the shoes of the enemy. The enemy hears a big debate in the United States, and they have to wonder — 'maybe all we have to do is wait and we'll win,'" he added.

That argument isn't flying with Rep. John Murtha, ranking Democrat on the House Defense Appropriations Subcommittee, who said Sunday that U.S. troops are no longer in a military action and by remaining, the United States is not giving the Iraqis any incentive to learn to defend themselves.

"We can't win this militarily. The military has done everything they can do. So, now it's up to the politicians, up to us in Congress — only we can send people to war. And it's up to us to find a way to solve this very difficult problem," he said, adding that he is "absolutely convinced that we're making no progress at all.

"Until we turn it over to the Iraqis, we're going to continue to do the fighting. Our young men and women are going to continue to suffer," Murtha said.

Murtha, a Pennsylvania Democrat and decorated Marine Corps veteran who served in the Vietnam War, last week urged the withdrawal of all U.S. troops within six months. His speech touched off a fierce debate between Republicans and Democrats, even leading one representative, Republican Jean Schmidt of Ohio to deliver a message from a representative and former Marine from her state.

"He also asked me to send Congressman Murtha a message that cowards cut and run; Marines never do," Schmidt said. "Danny and the rest of America and the world want the assurance from this body that we will see this through."

Since that bitter initial reaction from Republicans, including the White House, President Bush and others have tried to set a softer tone when it comes to Murtha, who strongly supported the Persian Gulf War in 1991 and voted to go into Iraq in October 2002.

"John Murtha is a good man, he also happens to be a good friend," Sen. Saxby Chambliss, R-Ga., told FOX News. "But this is one issue where (we disagree) ... if we pull out of Iraq in the short term we're not going to leave that country with the ability to secure itself."

Traveling in China, Bush also praised Murtha, but called him wrong.

"Congressman Murtha is a fine man, a good man, who served our country with honor and distinction as a Marine in Vietnam and as a United States congressman. He is a strong supporter of the United States military. And I know the decision to call for an immediate withdrawal of our troops by Congressman Murtha was done in a careful and thoughtful way," Bush said.

"I disagree with his position. An immediate withdrawal of our troops from Iraq will only strengthen the terrorists' hand in Iraq, and in the broader War on Terror. That's the goal of the enemy. They want to break our will in Iraq, so that we leave and they can turn Iraq into what Afghanistan was under the Taliban, a safe haven for terror, a place where they can plot and plan attacks against America and freedom-loving countries around the world," he added.

Murtha's speech Thursday calling for withdrawal set off a political battle on Capitol Hill that led to a bipartisan Senate vote against calling for a quick U.S. troop withdrawal. Sen. Joe Biden, D-Del., a potential 2008 presidential contender, told FOX News Sunday that he agreed that immediate withdrawal is not the answer, but he does think the goals in the war need to be redefined.

"You change the mission. The mission for us is keep Iraq from becoming a haven for terror and having a standup government where each of the major parties thinks they have a stake in the outcome ... not the democratization of Iraq to a liberal democracy, not the protection of every Iraqi citizen, et cetera. So mission dictates the number of troops," Biden said.

Rumsfeld said that the immediate mission is to prepare for the Dec. 15 election, in which a new Parliament will be chosen. In preparation for that election, the number of troops has risen to 159,000 from 138,000. Rumsfeld said that when the Dec. 15 election is finished, the number of U.S. troops will likely go back down to the "baseline" of about 138,000.

On the ground in Iraq, Col. Edward Cardon of the 3rd Infantry Division said that his troops are helping Iraqi soldiers prepare for the Dec. 15 election, and that they expect a very high turnout. He added that while a lot of threats of violence were made in two prior elections this year, they never materialized.

"The troops really are focused on the 15th of December elections. We have a lot of work to do to train the Iraqi security forces," Cardon told FOX News, adding that the goal is to "make as secure an environment as possible."

The secretary said that after the election is complete, U.S. troops will continue transferring security responsibility to the Iraqis. Rumsfeld said he will follow the recommendations of U.S. military commanders on the ground when it comes to additional reductions in the future.

Rumsfeld did not expressly deny the assertion that only about 800 Iraqi soldiers are prepared for "level one" operations, meaning they are able to go into combat operations by themselves. He did say, however, that out of the 212,000 Iraqi security forces, the overwhelming majority are involved in providing security for the Iraqi people, and about 100 battalions are engaged in repelling terror attacks.

"We've turned over something like 17 bases to the Iraqis recently. The Iraqis are in charge of one entire province. They're in charge of a big chunk of Baghdad currently," he added.

Cardon added that two Iraqi battalions are standing on their own, but four more are almost up and running and two could be ready before the Dec. 15 election, in which Iraqi security forces will take the lead in protecting voting stations.

While the numbers continue to change, Bush said from China that the Iraqis need to be able to protect themselves before U.S. military operations there are complete.

"Leaving prematurely will have terrible consequences, for our own security and for the Iraqi people. And that's not going to happen so long as I'm the president. This is a debate worthy of our country; it's an important debate. It does not have to be a partisan issue," Bush said.

But referring to partisanship, Murtha predicted that U.S. troops would be out of Iraq in substantial numbers by Election Day 2006.

FOX News' Megyn Kendall, Mike Emanuel and Sharon Kehnemui Liss contributed to this report.