More than 1 million Americans have selected health plans through the state and federal insurance exchanges to date under the Affordable Care Act, President Obama announced at an end-of-year press conference.

"For all the challenges we've had and all the challenges that we've been working on diligently in dealing with both the ACA and the website these past couple months, more than half a million Americans have enrolled through healthcare.gov in the first three weeks of December alone," Obama told reporters in the White House briefing room, speaking about the vastly improved federal insurance portal.

The figures reflect a significant uptick in enrollments this month, following the resolution of many technical glitches with the website in November, stepped-up outreach by health care advocates, and consumer interest in picking a plan before Monday's deadline to get coverage effective Jan. 1.

The administration had previously reported that roughly 365,000 people selected health plans on the exchanges in October and November. The nonpartisan Congressional Budget Office had projected that 7 million Americans would sign up by March 31.

Many of the 14 states plus D.C. which operate their own exchanges have been reporting a surge of sign-ups in December. Consumers have until 11:59 pm local time on Dec. 23 to select a plan in order to secure coverage in January. The first premium payment, which is required to finalize coverage, is due no later than Jan. 10, major insurers said this week.

"All told, millions of Americans, despite the problems with the website, are now poised to be covered by quality affordable health insurance come New Year's Day," Obama said.

Earlier Friday, HealthCare.gov experienced an hourslong unscheduled outage, prompting the once familiar error message 'The System is Down at the Moment" notice on the site.

"This system is in place while the tech team works on fixing an error that happened during routine maintenance last night," said Health and Human Services spokeswoman Joanne Peters. "This work started at 10 a.m. and we anticipate this could take two to three hours and that the site will be up and running again soon."

HHS officials said Monday that the online marketplace has been running "smoothly for the vast majority of consumers" and providing a "good consumer experience." The average error rate was less than one percent and system response time averaged around 500 milliseconds, they said.