Mayor Bloomberg is inserting himself into the central debate of the 2008 presidential campaign, casting the legislation Democrats are backing in Congress to set a timetable for withdrawing troops from Iraq as irresponsible.

The move puts Mr. Bloomberg’s stance on how to handle the war squarely at odds with that of senators Clinton and Schumer, who both voted for legislation that would require starting a withdrawal of troops in 120 days, and a goal of having all troops out of Iraq by March 31, 2008.

Mr. Bloomberg called the legislation in Congress “untenable” and said it is not in the country’s interest to declare a date to withdraw troops. He said the decision about how to handle the current situation in Iraq should have nothing to do with the ongoing political debate about whether America should have invaded in the first place.

“We ask our young men and women to go over and to fight, and if you have a deadline knowing they’re pulling out, how can you expect them to defend this country? How can you expect them to go out and put their lives at risk?” he said during a news conference on Staten Island yesterday morning.

“I just think that’s untenable and that this is not a responsible piece of legislation,” he said. “It is totally separate of how we’re conducting the war. It’s totally separate of whether we should have been there. The issue that you asked about is plain and simple: Should the Congress pass a law forcing the president to withdraw troops at a given point in time? I think that is not something that is in the country’s interest or in the military’s interest.”

While the mayor sidestepped stating his view of the war itself, his comments offer a window into his foreign policy thinking and depart from his on-again, off-again rule about sticking only to subjects that affect strictly New York City.

Political analysts say that coming out against the timetable also allows him to reserve a spot for himself on the national stage should he opt to run for president as an independent in 2008. They say his stance against the timetable is not only significant because it is yet another policy area where he is moving beyond the scope of issues that directly affect the five boroughs, but also because it could play into his political strengths as a non-partisan technocrat if he makes a bid for the White House.

“It’s almost like he’s defining the war as a management issue,” a professor of public administration at Columbia University, Steven Cohen, said. “He’s separating the policy issue from the management issue. That makes sense because his main advantage as a political figure is his expertise as a manager.”

Mr. Bloomberg has publicly said he does not plan to run for president, but many say he is taking a wait-and-see approach behind closed doors. His comments on the troop withdrawal align him with the three leading Republican presidential candidates — Mayor Giuliani, Senator McCain, and a former Massachusetts governor, Mitt Romney — and pit him against all of the leading Democratic presidential candidates, including Mrs. Clinton.

Earlier this week, Mr. Giuliani called a timetable a “terrible mistake” and said telling the enemy when to expect a military retreat “makes no sense.” Mrs. Clinton, who voted to authorize the war, said on Good Morning America the other day that the legislation invokes a “realistic timetable.”

The former first lady has been getting grilled on her position on the war in campaign stops throughout the country. She says she’ll end the war if elected president, but maintains that some special forces will have to remain.

While the other Democrats vying for the party’s nomination have also changed their positions over time, Mrs. Clinton is the one most recently on record as having opposed a definitive timeline to bring the troops home, notwithstanding her recent vote.

The mayor has come out against a timetable in the past, arguing that “you can’t have your soldiers over there fighting and dying where the enemy knows that all they’ve got to do is outwait them and build up public pressure by killing more of them.” But his decision to enter the fray on the legislation comes during the most heated week of debate about the Iraq war in Congress to date.

The Democratic-controlled Congress is inching closer to passing legislation that ties the funding that President Bush wants for the war efforts to the mandatory withdrawal date. Mr. Bush has vowed to veto the measure and has said he is confident that Congress will not have the votes to override him.

Mr. Bush said yesterday that setting a “specific and random date of withdrawal would be disastrous.”

“The clock is ticking for our troops in the field. Funding for our forces in Iraq will begin to run out in mid-April. Members of Congress need to stop making political statements, and start providing vital funds for our troops,” Mr. Bush said. “If Congress fails to pass a bill to fund our troops on the front lines, the American people will know who to hold responsible.”

Rep. Anthony Weiner, a Democrat who is hoping to replace Mr. Bloomberg in 2009, defended the timeline yesterday, saying in a statement: “To continue the open-ended commitment of our troops is what is not responsible.”

Governor Spitzer has opposed a timetable to withdraw from Iraq, according to a report in the New York Times.

Mr. Bloomberg had his own take on who should replace him when he is term-limited out of office in 2009. And while he may not be on board with Mrs. Clinton’s position on Iraq, he had nice things to say about her husband, President Clinton, when asked if he was going to encourage anyone from the private sector to enter the race to replace him.

He said Mr. Clinton is the only one who can say he’s run an operation the size of the city’s government.

“I’m not promoting the candidacy of Bill Clinton,” Mr. Bloomberg said. “But he can legitimately say he ran something that size. Nobody else can be able to say that.”