WASHINGTON — Democratic Party leaders agreed Saturday to seat Michigan and Florida delegates with half-votes at this summer’s convention with a compromise that left Senator Obama on the verge of the nomination but riled Senator Clinton’s backers, who threatened to fight to the August convention.

“Hijacking four delegates is not a good way to start down the path of party unity,” said her adviser Harold Ickes.

Senator Clinton’s camp maintains she was entitled to four additional Michigan delegates.

The decision by the party’s Rules Committee raised slightly the total delegates Senator Obama needs to clinch the nomination. Senator Clinton’s advisers conceded privately he will likely hit the magic number after the final primaries are held Tuesday night, but said the ruling threatened to dash any hopes of a unified party.

“Mrs. Clinton has told me to reserve her right to take this to the Credentials Committee” at the convention, Mr. Ickes, who is a member of the Rules Committee that voted Saturday, said.

The resolution increased the number of delegates needed to clinch the nomination to 2,118, leaving Senator Obama just 66 delegates away from the majority needed to secure the nomination.

“Our main goal is to get this resolved so we can focus on winning Michigan and Florida,” Senator Obama said while campaigning in South Dakota. “There were compromises. … I’m glad the DNC worked it through and I hope we can start focusing on substance as opposed to process.”

The deal was reached after committee members deliberated for nine hours, including three where they met privately and argued fiercely over their eventual deal, according to several people inside. They voted in front of a raucous hotel ballroom that frequently interrupted proceedings and reflected deep divisions within the party.

“How can you call yourselves Democrats if you don’t count the vote?” one of the many hecklers in the audience yelled loudly and repeatedly before being escorted out by security. “This is not the Democratic Party!”

A senior Clinton adviser, speaking on a condition of anonymity about internal campaign decisions, said the decision could be used to help her raise campaign donations for a scaled-down campaign that might focus on a signature issue — such as health care reform — rather than a traditional fight for the nomination.

The advisers said no decisions had been made, and it was still possible that said Senator Clinton would bow out once Senator Obama goes over the top.

Senator Clinton and her supporters wanted the Michigan and Florida delegations fully restored, according to January primaries that she won. But those contests were not recognized by the party because they were held too early, and both candidates agreed at the time they would not count.

But as Senator Clinton tried to catch up to Obama’s delegate lead, she has argued that the votes of the 2.3 million people who participated in the elections must be recognized.

Senator Obama’s supporters argued that they did compromise by allowing her to take the majority of delegates in two contests where he didn’t campaign.

The sticking point was Michigan, where Senator Obama’s name was not on the ballot.

Senator Clinton’s camp insisted Senator Obama shouldn’t get any pledged delegates in Michigan since he chose not to put his name on the ballot, and she should get 73 pledged delegates with 55 uncommitted. Senator Obama’s team insisted the only fair solution was to split the pledged delegates in half between the two campaigns, with 64 each.

The committee agreed on a compromise offered by the Michigan Democratic Party that would split the difference, allowing Senator Clinton to take 69 delegates and Senator Obama 59. Each delegate would get half a vote at the convention, according to the deal.

The deal passed 19-8. Thirteen members of the committee had endorsed Senator Clinton for president, so she wasn’t even able to keep her supporters together.

Allan Katz, a Rules Committee member and Obama supporter, said the Obama campaign had enough votes on the committee to support the campaign’s proposal to split the delegates 50-50 in Michigan. Ultimately, the campaign agreed instead to support the compromise negotiated by the Michigan Democratic Party as a way to resolve the matter.

“The ironic thing is Obama had the majority of that committee,” Mr. Katz said. “The Obama campaign wants to move on and compromise. We did not muscle our way through it. It was a wise decision from a well run and wise campaign that will reverberate.”

But the irate reaction from Senator Clinton’s campaign and her supporters in the sharply divided audience shows Senator Obama will have a long way to go to bring the party together after a long and divisive primary.

“We just blew the election!” a woman in the audience shouted. The crowd was divided between cheering Obama supporters and booing Clinton supporters.

“This isn’t unity! Count all the votes!” another audience member yelled.

Jim Roosevelt, co-chair of the committee, tried repeatedly to gavel it to order. “You are dishonoring your candidate when you disrupt the speakers,” he chided.

There are three primaries left in the contest — Puerto Rico on Sunday and Montana and South Dakota on Tuesday. Senator Obama should get at least 30 delegates in the remaining primaries, meaning he has to pick up no more than about 30 more superdelegates even if he loses Puerto Rico and South Dakota.

He will not clinch the nomination this weekend, barring a barrage of superdelegates Sunday.

The committee also unanimously agreed to seat the Florida delegation based on the outcome of the January primary, with 105 pledged delegates for Senator Clinton and 67 for Senator Obama, but with each delegate getting half a vote as a penalty.

Proponents of full seating continuously interrupted the committee members as they explained their support of the compromise, then supporters of the deal shouted back.

“Shut up!” one woman shouted at another.

“You shut up!” the second woman shouted back.

Senator Obama picked up a total of 32 delegates in Michigan, including superdelegates who have already committed, and 36 in Florida. Senator Clinton picked up 38 in Michigan, including superdelegates, and 56.5 in Florida. Senator Obama’s total increased to 2,052, and Senator Clinton had 1,877.5.

A proposal favored by Senator Clinton that would have fully seated the Florida delegation fully in accordance with the January primary went down with 12 votes in support and 15 against.

Tina Flournoy, who led Senator Clinton’s efforts to seat both states’ delegations with full voting power, said she was disappointed by the outcome but knew the Clinton position had “no chance” of passing the committee.

“I understand the rules. … I can tell you one thing that has driven these rules was being a party of inclusion,” Flournoy said. “I wish my colleagues will vote differently.”

Alice Huffman, a Clinton supporter on the committee, explained that the compromise giving delegates half votes was the next best thing to full seating.

“We will leave here more united than we came,” she said.

Some audience members heckled her in response. “Lipstick on a pig!” one shouted.