HONOLULU — A December surge propelled health care sign-ups through the government’s rehabilitated website past the 1 million mark, the Obama administration said Sunday, reflecting new vigor for the problem-plagued federal insurance exchange.

Of the more than 1.1 million people now enrolled, nearly 1 million signed up in December, with the majority coming days before a pre-Christmas deadline for coverage to start in January. Compare that with a paltry 27,000 in October, the federal website’s first, error-prone month — or 137,000 in November.

“We experienced a welcome surge in enrollment as millions of Americans seek access to affordable health care coverage,” Marilyn Tavenner, the head of the Centers for Medicare and Medicaid Services, said in a blog post.

The figures don’t represent a full accounting for the country. They don’t include December results from the 14 states running their own websites. Overall, states have been signing up more people than the federal government has. But most of that has come from high performers such as California, New York, Washington, Kentucky and Connecticut. Some states continue to struggle.

Still, the end-of-year spike suggests that the federal exchange serving 36 states is starting to pull its weight. The windfall comes at a critical moment for President Barack Obama’s sweeping health care law, which becomes “real” for many Americans on Jan. 1 as coverage through the exchanges and key patient protections kick in.

The administration’s concern now shifts to keeping the momentum going for sign-ups, and heading off problems that could arise when people who’ve already enrolled try to use their new insurance.

“They’ve got the front end of the system working really well,” said insurance industry consultant Robert Laszewski. “Now we can move on to the next question: Do people really want to buy this?”

The fledgling insurance exchanges — online markets for subsidized private coverage — are still likely to fall short of the administration’s own targets for 2013. That’s a concern because Obama needs millions of mostly younger, healthy Americans to sign up to keep costs low for everyone. Officials had projected more than 3.3 million overall would be enrolled through federal and state exchanges by the end of the year.

Tavenner said fixes to the website, overhauled to address widespread technical problems, contributed to December’s figures. But things haven’t totally cleared up. Thousands of people wound up waiting on hold for telephone help on Christmas Eve for a multitude of reasons, including technical difficulties.

“We have been a little bit behind the curve,” acknowledged Rep. Joaquin Castro, D-Texas, whose state has the highest proportion of uninsured residents. Nonetheless, the strong December sign-ups send a message. “The Affordable Care Act is something that’s good for the country,” said Castro.

“Obamacare is a reality,” conceded one of the law’s opponents, Rep. Darrell Issa, R-Calif., who as House oversight committee chairman has been investigating the rollout problems. However, he predicted it will only pile on costs.

“The fact that people well into the middle class are going to get subsidies is going to cause them to look at healthcare…sort of in a Third World way of do we get subsidies from the government for our milk, for our gasoline and, oh, by the way, for our healthcare,” said Issa.

For consumers who successfully selected one of the new insurance plans by Dec. 24, coverage should start on New Year’s Day. That’s provided they pay their first month’s premium by the due date, extended until Jan. 10 in most cases.

But insurers have complained that another set of technical problems, largely hidden from consumers, has resulted in the government passing along inaccurate data on enrollees. With a flood of signups that must be processed in just days, it remains unclear whether last-minute enrollees will encounter a seamless experience if they try to use their new benefits come Jan. 1.

The White House says the error rate has been significantly reduced, but the political fallout from website woes could pale in comparison with the heat that Obama might take if Americans who signed up and paid their premiums arrive at the pharmacy or the emergency room and find there’s no record of their coverage.

Officials are also working to prevent gaps in coverage for at least 4.7 million Americans whose individual policies were canceled this fall because they fell short of the law’s requirements. The administration has said that even if those individuals don’t sign up for new plans, they won’t face the law’s tax penalty for remaining uninsured.

The new enrollment figures were released Sunday while Obama was vacationing in Hawaii. Although the president has spent most of his time relaxing with friends and family, he stepped into work mode late Friday for an update from aides on his signature domestic policy achievement. The White House said Obama told his team to focus on minimizing disruptions for those switching plans.

A few states offering their own updates have also posted encouraging totals, including New York, where more than 200,000 have enrolled either through the state exchange or through Medicaid, a government program expanded under Obama’s health law to cover more people. In California, a tally released Friday showed nearly 430,000 have enrolled through the exchange so far.

A full 50-state enrollment report is due next month. Overall, the goal is to sign up 7 million people before the first-year open enrollment period closes at the end of March.

Castro and Issa spoke on NBC’s “Meet The Press.”

Associated Press writer Ricardo Alonso-Zaldivar in Washington contributed to this report.

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