House Democrats are structuring the supplemental funding bill to give the next president the flexibility to make broad changes in U.S. war policy, a senior appropriator and war critic said Thursday.

James P. Moran, D-Va., said the bill would ensure that an expected $70 billion “bridge fund” for the wars in Iraq and Afghanistan would not become available to the Pentagon until fiscal 2009 begins in October, only a month before the 2008 elections.

Moran, who backs Sen. Barack Obama’s bid for the Democratic presidential nomination, said a flexible bridge fund could, for example, allow the next president upon taking office to shift large amounts of money away from Iraq to Afghanistan or pay for troop withdrawals.

“I wouldn’t be at all shocked if President Obama might shift some of the Iraq money to Afghanistan,” said Moran, adding that a majority of members on the Defense Appropriations Subcommittee would support such a move.

The House Appropriations Committee is working with the Pentagon to add details to the bridge fund, which Democrats intend to offer along with the $102.5 billion outstanding fiscal 2008 request for military spending. The bridge fund will be detailed but will give the new president enough flexibility to begin withdrawing troops immediately after inauguration, Moran added.

Moran’s remarks reflected the relatively small area of unity among Democrats over the bill, which party leaders are still crafting amid broad disagreement within the caucus over how to handle other spending and policy issues.

House Majority Leader Steny H. Hoyer, D-Md., said that adding a number of additional items to the supplemental, such as food stamps and unemployment insurance, remained under discussion.

“It’s not so much that we’re having difficulty,” Hoyer said. “We’re trying to agree, and trying to weigh what we want to do, and how expensive we want to make it.”

Democrats are also likely to split the bill up to allow for separate votes on war funding, a timeline for withdrawal, domestic items and a package of tax incentives for renewable energy, according to a senior House aide.

“I don’t think it will be two or three bills. One bill,” Hoyer said. “But there may be three amendments or four amendments or five amendments.’’

Hoyer said that it was still his intention to pass the bill in time for the Senate to act and for President Bush to sign it before the Memorial Day break. “We are discussing how to process the supplemental,” he said on the House floor.

But he did not say whether the bill would go through committee or come directly to the floor, or if the measure would come to the floor next week, as had been his hope.

Splitting the supplemental to allow separate votes on the war funding and other items would not be unprecedented. Last May, the House held two votes on the fiscal 2007 supplemental bill (PL 110-28) — one on an amendment that provided $22.2 billion for domestic funding not requested by Bush and another on an amendment that included $97.8 billion, mostly for war funding.

The package was then sent to the Senate, where it was cleared for the president. The two-step approach allowed anti-war Democrats to vote against the military funding but for the domestic spending.

Although House Democrats have signaled that they plan to exceed President Bush’s total $108 billion request by including other items, they appeared to be working toward limiting the domestic spending to items that could attract Republican support. They are also considering adding a package of education benefits for veterans, a limited extension of unemployment insurance and language blocking Bush administration rules designed to reduce federal Medicaid costs.

House Republicans have expressed their preference for a bill limited to funding the war.

“I’ve seen five different plans in the last four days,” said House Minority Leader John A. Boehner, R-Ohio. “We’re going to insist that this is about funding the troops, and nothing else.”

The Senate, for its part, has taken a wait-and-see approach, deferring action until the House moves legislation. But Senate Majority Leader Harry Reid, D-Nev., who met with House Appropriations Chairman David R. Obey, D-Wis., Thursday morning to discuss supplemental strategy, indicated his support for adding the Medicaid language.

The Senate will hold votes on war policy, Reid said, although he did not specify which amendments would be granted floor time.

Democrats also remained tight-lipped as to whether they would allow the supplemental to pass through committee or head directly to the floor, as has been discussed. Republicans have warned that an attempt to circumvent the committee would lead to a huge fight on the floor, led by GOP appropriators.

In a colloquy with Hoyer Thursday, Minority Whip Roy Blunt, R-Mo., noted that the House has considered 36 supplementals since 1989 and all but seven went through committee. “Members of the committee have expressed great concern if this is not marked up in regular order. It is fairly extraordinary,” Blunt said.

“I understand the committee’s concern,” replied Hoyer, a former longtime Appropriations Committee member. “We are trying to proceed in a way that will facilitate final passage.’’

Jerry Lewis of California, the ranking Republican of the committee, sent a second letter to Obey Thursday in which he again stressed the opposition of the GOP appropriators to bypassing the committee.

“For the record, under the GOP majority, the Democrat minority offered and had roll call votes on 46 individual amendments during full Committee consideration of Emergency Supplemental bills from 1995-2006. How can you disregard this precedent?” Lewis wrote.

Earlier this week, Lewis decried the lack of consultation with the minority and warned that bypassing the committee would put most GOP appropriators “in the revolution business. I don’t know what that means, but they would be.”

Republican appropriator Mike Simpson of Idaho said that skipping a markup might lead Republicans to bring floor action to a standstill by offering motions to adjourn and other procedural motions.

Republicans used a similar tactic last year when Obey tried to bring an appropriations bill to the House floor without including earmarks, saying he would provide them after House passage but before conference.

Alan K. Ota and Edward Epstein contributed to this story.