Democrats are close to unveiling their complex strategy for the supplemental spending bill, but their plan to speed its passage faces a number of obstacles.

With the hope of streamlining the process and finishing work on the measure by the Memorial Day recess, Democrats have signaled that their strategy for the supplemental could bypass both Appropriations committee markups and even a House-Senate conference on the bill.

But Republicans and even some Democrats are opposed to such a strategy, saying that if too many lawmakers are left out of the process, the result could be even longer delays in the bill’s enactment.

After weeks of discussions, several House aides confirmed that they could bring to the floor, probably next week, a bill that would be open to three specific amendments: one for over $170 billion in war funding, another for domestic spending items and a third for a series of Iraq-related policy provisions.

The bill would then be packaged and sent to the Senate, which would hold floor votes on its own amendments and send the measure back to the House to be cleared.

Daniel K. Inouye, D-Hawaii, the chairman of the Defense Appropriations Subcommittee, said House and Senate Democrats were closing in on an agreement. “I think we’re about 95 percent there,” Inouye said.

But after a leadership meeting Tuesday evening, House Majority Leader Steny H. Hoyer, D-Md., said no final deal had been struck. “There are still a lot of moving parts,” Hoyer said.

In their effort to appease various factions within their caucus by separating votes on the war and domestic spending and then combining them after the fact, House Democratic leaders could produce a bill incapable of garnering the 60 votes needed in the Senate or of getting signed by President Bush.

House Minority Whip Roy Blunt, R-Mo., called the Democratic plan “too cute by half” and complained that by possibly eliminating both the markup and conference processes, Democrats were suppressing the rights of the minority and forcing Republicans to use procedural tactics to bring the Congress to a halt.

“I think they’re doing it partly because they are afraid their ideas won’t stand the test of competing ideas,’’ Blunt said. “They are threatening to burn the House down.”

If Democrats were successful in using this strategy to get the supplemental bill to the president, Bush would surely veto it, and Republicans would sustain the veto, Blunt said. That would force Congress to take up the bill again in June.

Senate Republicans were equally incensed and pledged to fight back against their exclusion from the process.

“They’re telling us that they’re going to bypass the committee structure. . . . I believe it’s unconstitutional,” said Ted Stevens of Alaska, the ranking Republican on the Senate Appropriations Defense Subcommittee.

Some senior Senate Democrats also were not happy with House strategy. Appropriations Chairman Robert C. Byrd, D-W.Va., is leading a “vociferous opposition” to bypassing the normal conference process, according to a Senate Democratic aide.

Byrd and other Senate critics are concerned that the established process for appropriating emergency funds would be blown apart — all to save a week or two of work on a bill that could be finished before the Memorial Day recess anyway, the aide said.

Senate Republican appropriators wrote Byrd on Tuesday to express their “grave concerns” with the proposed plan to forgo a committee markup.

“We were not consulted prior to the initiation of this plan late last week, and we believe that such a closed-door approach — which purposefully limits opportunities to offer amendments — scuttles the ability of the Senate fully and fairly to debate vital national security matters,” they wrote.

The 13 Republican appropriators — all except for Minority Leader Mitch McConnell of Kentucky, who was copied on the letter, along with Majority Leader Harry Reid, D-Nev. — asked that the committee hold a markup no later than the end of this week, regardless of what the House does.

Meanwhile, Sen. Pete V. Domenici, R-N.M., predicted that Democrats will save no time by cutting House Appropriations out of the deliberations.

“The Senate will be very upset because the committee had no shot at it, so there will be lots of amendments” when it reaches the Senate floor, Domenici said.

Meanwhile, Democrats were still negotiating Tuesday evening among themselves over what policy prescriptions and domestic spending items to add to the supplemental.

Carl Levin, D-Mich., Senate Armed Services chairman, said he had submitted language to party leaders that would set a goal of troop withdrawals within a certain time frame. But he said the House’s version of the bill was likely to contain such language.

One House Democratic aide said the domestic spending section probably would include Bush’s fiscal 2009 request for levee repairs, which is about $6 billion, as well as about $2 billion in other domestic spending, although that section has not been finalized. Leaders also are strongly considering including an extension of unemployment insurance benefits, a recently passed Medicaid bill, a bill to increase veterans’ educational benefits, and tax incentives for renewable energy.

Backers of transforming Iraqi reconstruction grants to loans also say they have been promised binding language in the supplemental, but that hasn’t been finalized.

Another House Democratic aide said at least one year’s worth of the funding for veterans’ benefits, estimated at between $2.5 billion and $4 billion, would be included in the domestic spending portion of the legislation. The veterans’ measure is a “virtual certainty” for inclusion, Sen. Charles E. Schumer, D-N.Y., told reporters Tuesday.

At a White House news conference Tuesday, Bush expressed a willingness to negotiate over money for veterans but refused to budge on his threat to veto the bill if it exceeds the $108 billion he requested or if it sets timelines for troop withdrawals.

“$108 billion is $108 billion,” Bush said. “I made my position very clear to Congress, and I will not accept a supplemental over $108 billion, or a supplemental that micro-manages the war, [or] ties the hands of our commanders.”

Liriel Higa, Kathleen Hunter, Jonathan Allen, David Clarke, Edward Epstein, Kerry Young and Adam Graham-Silverman contributed to this story.