WASHINGTON — Triumphant Democrats steered landmark health care legislation to the brink of passage in the House late Saturday night, spurred by a summons from President Barack Obama to “answer the call of history” and expand coverage to millions who lack it.

After months of struggle, Speaker Nancy Pelosi projected confidence and likened the bill to the creation of Social Security in 1935 and Medicare 30 years later.

“It provides coverage for 96 percent of Americans. It offers everyone, regardless of health or income, the peace of mind that comes from knowing they will have access to affordable health care when they need it,” said Rep. John Dingell, the 83-year-old Michigan lawmaker who has introduced national health insurance in every Congress since succeeding his father in 1955.

In the runup to a final vote, conservatives from the two political parties joined forces to impose tough new restrictions on abortion coverage in insurance policies to be sold to many individuals and small groups. They prevailed on a roll call of 240-194.

Ironically, that only solidified support for the legislation, clearing the way for conservative Democrats to vote for it.

Passage would clear the way for a Senate debate expected to begin in several days. Democratic leaders have been working on a self-imposed deadline for passing a final compromise, but Senate Majority Leader Harry Reid signaled recently that may slip.

United in opposition to the health care bill, minority Republicans cataloged their objections across hours of debate on the 1,990-page, $1.2 trillion legislation.

“We are going to have a complete government takeover of our health care system faster than you can say, ‘this is making me sick,”’ jabbed Rep. Candice Miller, R-Mich., adding that Democrats were intent on passing “a jobs-killing, tax-hiking, deficit-exploding” bill.

But with little or no doubt about the outcome, the rhetoric lacked the fire of last summer’s town hall meetings, when some critics accused Democrats of plotting “death panels” to hasten the demise of senior citizens.

The legislation would require most Americans to carry insurance and provide federal subsidies to those who otherwise could not afford it. Large companies would have to offer coverage to their employees. Both consumers and companies would be slapped with penalties if they defied the government’s mandates.

Insurance industry practices such as denying coverage on the basis of pre-existing medical conditions would be banned, and insurers would no longer be able to charge higher premiums on the basis of gender or medical history. In a further slap, the industry would lose its exemption from federal antitrust restrictions on price gouging, bid rigging and market allocation.

At its core, the measure would create a federally regulated marketplace where consumers could shop for coverage. In the bill’s most controversial provision, the government would sell insurance, although the Congressional Budget Office forecasts that premiums for it would be more expensive than for policies sold by private firms.

The bill is projected to expand coverage to 36 million uninsured, resulting in 96 percent of the nation’s eligible population having insurance.

To pay for the expansion of coverage, the bill cuts Medicare’s projected spending by more than $400 billion over a decade. It also imposes a tax surcharge of 5.4 percent on income over $500,000 in the case of individuals and $1 million for families.

The bill was estimated to reduce federal deficits by about $104 billion over a decade, although it lacked two of the key cost-cutting provisions under consideration in the Senate, and its longer-term impact on government red ink was far from clear.

Democrats lined up a range of outside groups behind their legislation, none more important than the AARP, whose support promises political cover against the cuts to Medicare in next year’s congressional elections.

The nation’s drug companies generally support health care overhaul. And while the powerful insurance industry opposed the legislation, it did so quietly, and the result was that Republicans could not count on the type of advertising campaign that might have peeled away skittish Democrats in swing districts.

Over all, the bill envisioned the most sweeping set of changes to the health care system in more than a generation, and Democrats said it marked the culmination of a campaign that Harry Truman began when he sat in the White House 60 years ago.

Debate on the House floor had already begun when Obama strode into a closed-door meeting of the Democratic rank and file across the street from the Capitol to make a final personal appeal to them to pass his top domestic priority. While the session was private, he later said he had told the rank and file “that opportunities like this come around maybe once in a generation.... This is their moment, this is our moment, to live up to the trust that the American people have placed in us...”

“I urge members of Congress to rise to this moment. Answer the call of history, and vote yes for health insurance reform for America,” he said.

Participants also said Obama had referred to this week’s shooting rampage at Fort Hood, Texas, in which 13 people were killed. His remarks put in perspective that the hardships soldiers endure for the country are “what sacrifice really is,” as opposed to “casting a vote that might lose an election for you,” said Rep. Robert Andrews, D-N.J.

As drafted, the measure denied the use of federal subsidies to purchase abortion coverage in policies sold by private insurers in the new insurance exchange, except in cases of incest, rape or when the life of the mother was in danger.

Democratic abortion foes, joined by Republicans, won far stronger restrictions that would rule out abortion coverage except in those three categories in any government-sold plan. It would also ban abortion coverage in any private plan purchased by consumers receiving federal subsidies.

Disappointed Democratic abortion rights supporters grumbled about the turn of events, but appeared to pull back quickly from any thought of opposing the health care bill in protest.

One, Rep. Jan Schakowsky, D-Ill., detailed numerous other benefits for women in the bill, including free medical preventive services and better prescription drug coverage under Medicare. “Women need health care reform,” she concluded in remarks on the House floor.

Republicans offered an alternative that relied heavily on loosening regulations on private insurers to reduce costs for those who currently have insurance, in some cases by as much as 10 percent. But congressional budget analysts said the plan would make no dent in the ranks of the uninsured, an assessment that highlighted the difference in priorities between the two political parties. It fell by a near party line vote of 258-176.

It was a theme of Obama’s remarks to Democrats at midmorning.

The president said Democrats have a 70-year history of creating and defending programs like Social Security and Medicare, Andrews said afterward, adding Obama had said the day’s vote “is going to define the difference between the Republican and Democratic parties for decades.”