Hisham Uadadeh enrolls in a health insurance plan under the Affordable Care Act with the help of A. Michael Khoury at Leading Insurance Agency in Miami, Florida. (Joe Raedle/Getty Images)

More than 6 million Americans have signed up for private health insurance under the ­Affordable Care Act, the White House announced Thursday, ­reflecting a surge in enrollment after months of technical problems prevented many people from picking a plan.

The administration originally expected 7 million to buy health plans during the law’s initial six-month enrollment period but revised its target to 6 million after the disastrous rollout of HealthCare.gov, the federal Web site.

President Obama shared the new total in a conference call with thousands of health-care Web navigators and volunteers who are helping enroll people through state and federal market­places, urging them to redouble their efforts over the next few days. There were more than 1.5 million visits to the Web site and more than 430,000 calls to federal call centers Wednesday, administration officials said.

“We are seeing near record numbers of consumers coming to check out their options and enroll in coverage,” Marilyn ­Tavenner, head of the Centers for Medicare and Medicaid Services, said in a blog post.

The announcement comes in the final days of the health law’s maiden sign-up period, when the most controversial legislation in decades was aggressively promoted by the administration and vehemently fought by its opponents.

The Obama administration is courting a certain demographic as the enrollment deadline looms. So who’s on the receiving end of the last-minute hustle? (Pamela Kirkland/The Washington Post)

The final enrollment figure will not be known until next month, in part because this week the administration decided to give extra time to those who say they tried to enroll but failed to do so by the March 31 deadline.

In addition, not all of those who are signing up will pay for their plans, which determines whether they will actually be covered.

“Falling 1 million short of the proclaimed goal is nothing to celebrate — not to mention the White House still refuses to disclose the most important figure of who’s paid,” said Marsha Blackburn (R-Tenn.), vice chair of the House Energy and Commerce Committee. “As the administration scrambles to conceal its incompetence, millions of Americans are now enduring canceled health plans, higher premiums and lost access to trusted doctors.”

Still, the higher numbers show that many Americans are determined to get insured under the law, a process that’s become easier after an extended period in which technical glitches made it nearly impossible in many states.

The Department of Health and Human Services had expected 1.2 million people to sign up this month; enrollment has already reached 1.8 million.

“You can’t say, ‘Look, everybody hates the law,’ when you see these big numbers coming in,” said John Holahan, a fellow at the Urban Institute’s Health Policy Center, which has been conducting a series of surveys related to the Affordable Care Act.

Holahan added that it is still unclear what is driving the surge in sign-ups. Once people have plans, they may be split between those who like the benefits and those who find their out-of-pocket expenses and provider options unacceptable, he added.

ACA enrollment numbers, state-by-state

“We don’t know how much is the mandate and how much is people realizing it’s not a bad deal,” Holahan said.

Ballpark target figures such as 6 million — the figure the Congressional Budget Office projected last month — do not shed much light on how successful the program will be, according to Kaiser Family Foundation President Drew Altman, because the critical question is the mix between healthy and sick people on the exchange in a given state.

“While it is true that the greater the number of enrollees the higher the likelihood of a balanced risk pool, six million is not a magic number,” Altman wrote in a blog post Monday.

Conservatives argue that many Americans will remain un­insured after open enrollment ends and that the federal government will have to give insurance companies extra money to compensate for the fact that they are covering too many unhealthy — and therefore costly — enrollees.

“So the insurance industry is going to get a lot of money out of Obamacare one way or another, and 30 million people are going to remain uninsured,” said Dean Clancy, vice president of public policy at FreedomWorks, a conservative nonprofit group.

Federal officials have not released data on how many of the people in the federal exchanges have paid for plans, which will be crucial in determining the overall enrollment total.

But California, which runs its own exchange and accounts for about one-fifth of all enrollments, says it has a payment rate of 85 percent.

Anthony Wright, executive director of Sacramento-based Health Access, a health-care advocacy group, noted that California residents are persevering despite the fact that it takes between 30 and 50 minutes to get through to an operator at one of the state’s call centers. “It’s not like we’re glitch-free,” Wright said.

California has seen more Latinos and young people enroll in recent weeks, he added. “The demographics are shifting.”

The enrollment tally suggests that a range of efforts by the White House and its allies have begun to pay concrete dividends. The Service Employees International Union and its local affiliates have devoted between $6 million and $10 million to the union’s enrollment campaign.

The Texas Organizing Project, a grass-roots group that is partnering with the SEIU, has held major enrollment events in Texas’s three biggest urban counties each weekend this month, along with seven telethons with both English- and Spanish-language networks.

Tiffany Hogue, the director of the group’s health-care campaign, noted that enrollments in Harris County — which includes Houston — increased 40 percent in the week of March 10, compared with previous weeks this year.

“It’s getting people comfortable and increasing their confidence level,” she said.

After the March 31 deadline, uninsured Americans who ­haven’t qualified for an extension will face a tax penalty of $95 or 1 percent of their income, whichever is higher.

The new enrollment tally came as five centrist Democratic senators and an independent unveiled a package of proposals Thursday aimed at fixing some of the least popular aspects of the Affordable Care Act.

Among the measures are ones that would add a cheaper level of plans to the program’s offerings; provide additional funding and opportunities to establish insurance co-ops; allow coverage plans to be offered regionally and across state lines; streamline reporting requirements for employers; and make providing coverage optional for businesses with up to 100 employees.

Amy Goldstein contributed to this report.