The White House and labor unions unveiled a breakthrough deal Thursday to clear a major obstacle blocking President Barack Obama’s all-out campaign to remake US health care, his top domestic goal.

The announcement gave a much-needed boost to Obama and his Democratic allies as they strove in intense marathon talks to meld rival Senate and House of Representatives versions of legislation to enact the historic overhaul.

“We are on the doorstep” of a historic achievement, the president told Democrats in the House of Representatives as they held their annual retreat to map the way to November mid-term elections.

Democrats, eager for what would be a major victory, said they hoped to overcome the last hurdles to craft a final compromise by the weekend and pass it before the president’s State of the Union speech, just weeks away.

The party’s top leaders in Congress were expected to the White House well after nightfall to continue their intense, marathon talks, an Obama aide said.

Obama used his rare visit to the US Congress to try to steel the resolve of House Democrats worried about paying a price in November mid-term elections for backing the legislation.

“If Republicans want to campaign against what we’ve done by standing up for the status quo and for insurance companies over American families and businesses, that is a fight I want to have,” said the president.

Democrats working on the final compromise had next-to-no margin for error:

The Senate passed its bill on Christmas Eve by exactly the 60 votes needed and the House got just two more than the 218 needed seven weeks earlier.

But they took a critical step forward when labor unions announced a deal in which they accepted a watered-down version of the Senate bill’s new taxes on generous health plans — like those their members have — to fund the overhaul.

Union leaders told reporters on a conference call to unveil the accord that they would have preferred to go another route but that they would fight for the final bill and that the House and Senate had endorsed their approach.

“We think that everybody is on board with this,” said Richard Trumka, president of the largest US labor federation, the AFL-CIO. Gerry McEntee, who heads the largest union of government workers, said they and their Democratic allies were “ready to fight” for the bill.

Republicans, seemingly united in opposition to the plan, have said they plan to harness public doubts about the legislation ahead of the mid-term elections, in which a sitting US president’s party typically loses seats.

Several other disputes stood in the way of crafting a compromise that could be sent to the non-partisan Congressional Budget Office for a formal assessment of its likely impact, cost, and effect on the soaring US deficit.

A previous CBO score showed the legislation would have cut roughly 130 billion dollars off the deficit over the first 10 years.

The legislation, which would usher in the most sweeping overhaul of its kind in four decades, aims to extend coverage to more than 30 million of the

36 million Americans who lack health insurance and curb abusive practices by private insurers who provide most Americans’ coverage.

Recent public opinion polls have found deep skepticism about the bill, with a large segment disappointed that the sweeping legislation does not go far enough.

The White House and Democrats were also looking to resolve another dispute centered on whether health care “exchanges” — marketplaces where consumers could comparison-shop for coverage — would be national or state-by-state.

“We are very, very close” to agreeing on a final plan, said Obama spokesman Robert Gibbs.

The United States is the world’s richest nation but the only industrialized democracy that does not provide health care coverage to all of its citizens.

The United States spends more than double what Britain, France and Germany do per person on health care.

But it lags behind other countries in life expectancy and infant mortality, according to the Organization for Economic Cooperation and Development (OECD).