(Updates number, adds quote from Sebelius, edits)
By Susan Cornwell
WASHINGTON, Dec 31 (Reuters) - More than 2.1 million people have enrolled in private health insurance plans through new federal and state websites since they were launched in October as part of President Barack Obama's healthcare overhaul, U.S. officials said on Tuesday.
While short of the 3.3 million enrollees that the Obama administration was hoping for by now, the number signing up for insurance is a dramatic improvement from the early weeks of the program, when barely 150,000 got coverage because of a series of technical problems with the federal website HealthCare.gov.
Sign-ups for what has become known as Obamacare gained pace during December as the website's performance improved, and as more Americans focused on getting coverage by the new year.
Many of the newly insured under the Patient Protection and Affordable Care Act enrolled just ahead of a Dec. 24 deadline to receive benefits on Jan. 1, giving health insurers a tight framework to create accounts that can be accessed by doctors.
About half the 2.1 million signed up for private health insurance on the federal website, Health and Human Services Secretary Kathleen Sebelius told reporters in a conference call. HealthCare.gov covers 36 states; another 14 states and the District of Columbia have their own healthcare websites.
Sebelius said that in October and November, another 3.9 million Americans were determined eligible for Medicaid or the Children's Health Insurance Program, although this included some renewals. Both are government-run programs serving low-income people.
HealthCare.gov crashed soon after its launch on Oct. 1, as millions of visitors accessed the site, and remained balky for much of the ensuing weeks.
The disastrous rollout disappointed those who were trying to enroll in subsidized health insurance, and damaged the credibility of President Obama and his signature domestic policy achievement. Two officials have left the U.S. agency that was in charge of launching the website.
Administration officials hope they have turned a corner toward a better-working program that makes it possible for millions of Americans to get health insurance who did not have it before. People can still sign up until March 31 for coverage in 2014.
But the new year is expected to bring new challenges as many Americans begin to use their medical coverage for the first time. U.S. officials have said that some errors occurred with the transmission of enrollment data to insurers, especially early in the enrollment period.
"January 1st marks not only the beginning of a New Year, but an exciting new day in health care as millions of Americans will now be able to access care, thanks to the coverage they found at the Health Insurance Marketplace," Sebelius said in a blog posting on Tuesday.
"For many of the newly insured ... it will be the first time that they can enjoy the security that comes with health coverage," Sebelius said. She said the administration was doing everything possible to help with the transition period. (Editing by Jonathan Oatis and Bill Trott)