WASHINGTON—President Barack Obama summoned Democrats to “answer the call of history” Saturday as the House pushed toward a vote on a landmark health care bill holding out the promise of coverage for tens of millions who lack it.

After months of struggle, capped by a final clash over abortion, Speaker Nancy Pelosi predicted, “we will pass health care reform,” and likened the events to the creation of Social Security in 1935 and Medicare 30 years later.

United in opposition, 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.