WASHINGTON — Senator Clinton is urging the Pentagon to begin planning for an American troop withdrawal from Iraq, even as Democrats in Congress have backed off a demand that an exit timetable be tied to war funding.

Mrs. Clinton yesterday sent a letter to the defense secretary, Robert Gates, seeking assurances that military leaders had drawn up “contingency” plans so that American troops could pull out of Iraq without “unnecessary danger.” She cited recent reports that Iraqi military officials are making their own preparations in the event of a rapid American exit.

“In light of growing violence and insecurity in Iraq, the continued lack of political progress by Prime Minister al-Maliki, the Iraqi defense ministry’s level of contingency planning, and the will of the American Congress to begin withdrawing troops from Iraq, it is imperative that the Department of Defense prepare plans for the phased redeployment of U.S. forces,” Mrs. Clinton wrote.

Mrs. Clinton, a member of the Senate Armed Services Committee, said she also conveyed similar concerns in a private meeting with the chairman of the Joint Chiefs of Staff, Peter Pace.

“Withdrawal is very complicated. It doesn’t happen overnight,” Mrs. Clinton told reporters yesterday, saying she has heard that there has been “no, or very limited, planning” for a pullout. “If they’re not planning for it, it will be difficult to execute it in a safe and efficacious way.”

The Defense Department yesterday said it would not discuss correspondence with elected officials. Mr. Gates earlier this month said the department’s planning for alternatives to the current strategy in Iraq was “more of just broader conceptual thinking” rather than specific contingency plans involving a redeployment of troops.

Mrs. Clinton’s letter comes as Democratic lawmakers are facing mounting pressure from all corners of the party on Iraq. The Democratic leadership in Congress has backed off its insistence that a timetable for withdrawal be included in an emergency war funding bill, infuriating the party’s most fervently anti-war members.

The anti-war group MoveOn.org fired off a letter to its members urging them to call their representatives and demand that they “hold out for real accountability to end the war.” A Democratic presidential candidate, John Edwards, called the compromise a “capitulation” and is pushing lawmakers to “use every power” they have to stop the funding bill.

Mrs. Clinton dodged repeated questions yesterday about whether she will support the funding bill without an exit timeline. She refused to discuss the war at a press conference she held on immigration reform, telling reporters afterward: “When I have something to say, I’ll say it.”

Her top rival for the Democratic nomination, Senator Obama of Illinois, also has not said how he plans to vote on the bill.

The party’s two other candidates serving in the Senate, Christopher Dodd of Connecticut and Joseph Biden of Delaware, are split.

Mr. Dodd issued a statement yesterday saying he would vote against the funding. “I cannot and I will not simply give this president another blank check,” he said.

Mr. Biden also has called for the withdrawal of American troops, but he cited the “political reality” that Democrats cannot muster the votes to override another presidential veto. He said he would vote in favor of the funding bill. “I wish you could end it today,” Mr. Biden said. “But I’m not going to vote to leave the troops without money.”

Democrats are facing pressure not only from the anti-war wing of their party, but also from an elder Democratic statesman, Bob Kerrey, who is cautioning lawmakers against supporting a precipitous withdrawal from Iraq.

“American lawmakers who are watching public opinion tell them to move away from Iraq as quickly as possible should remember this: Concessions will not work with either al Qaeda or other foreign fighters who will not rest until they have killed or driven into exile the last remaining Iraqi who favors democracy,” Mr. Kerrey, a former Nebraska senator who is now president of the New School in Manhattan, wrote in an opinion column Tuesday in the Wall Street Journal. He added that “a unilateral withdrawal from Iraq would hand Osama bin Laden a substantial psychological victory.”

In an interview yesterday, Mr. Kerrey, who ran for president in 1992 and served on the September 11 commission, said he did not “have anybody particularly in mind” when writing the piece. He has not endorsed a candidate for president, and he declined to discuss in detail the Iraq positions of the various Democratic contenders.

What bothers him, he said, is the nature of the Iraq debate and the continued focus on the decision to go to war in the first place. “This isn’t the 2003 war,” he said. “That war is over. It ended. We got rid of Saddam Hussein. The current war is against the government of Iraq. The question is, are we an ally of Iraq? Are we going to help them?”

Mr. Kerrey’s words may serve as a warning to all of the Democratic presidential hopefuls, but they have particular implications for Mrs. Clinton, who has struggled more than any of her rivals to define her position on the war.

She has been increasingly vocal about the need to “end this war,” but she also has resisted proposals to cut off funding and has said she foresees keeping residual military forces in Iraq for some time. But in addition to calling attention to her letter to the Pentagon yesterday, she has introduced legislation to deauthorize the war — a move that was seen as an attempt to reach out to anti-war voters.

“She’s engaging in a very delicate balancing act,” a Democratic strategist, Daniel Gerstein, said. Mr. Gerstein has advised Senator Lieberman of Connecticut, an independent who caucuses with Democrats and is a staunch supporter of the war.

In a strategy typical in presidential politics, the New York senator is looking to satisfy the Democratic base while presenting herself as viable in a general election. “To win the general election,” Mr. Gerstein said, “whoever is the nominee is going to have to be credible on national security.”

Mrs. Clinton, he said, is “trying to stake out the responsible, centrist Democrat position in a rapidly anti-war electorate.”