Obama care has been launched on Tuesday but suffered from technical glitches and heavy Internet traffic.
However, the service started operating despite widespread government shutdowns, a consequence of the Congress’ failure to reach an agreement on the country’s budget.
Since its inception, the scheme has been criticised by Republicans and faced delays in building the technology infrastructure to support the scheme in 50 US states.
On the first day of operations the websites in 47 states were difficult to access, turning up frequent error messages and traffic overload notices.
According to Reuters, one frequently observed glitch involved a page asking the user to answer security questions that either went blank or would not accept new data. Kansas officials urged residents to wait a few weeks for the "bugs" to be worked out before enrolling.
The Department of Health and Human Services said 2.8 million people visited the federal HealthCare.gov since midnight, with 81,000 reaching out to call centres and 60,000 requesting live chats. The department did not provide details on the source of the traffic or the number of visitors who applied for health insurance, but said it was working to speed up the site.
"We think we're off to a good start," said Marilyn Tavenner, head of the Centers for Medicare and Medicaid Services, which oversees the new exchange.
The performance of state-run exchanges was mixed, with users in Connecticut, Rhode Island and California able to create profiles. Kentucky said it had processed more than 1,000 insurance applications, while Colorado said 1,300 user accounts had been created. Maryland delayed its launch by hours. When it went live, access stalled for some users.
The administration had predicted hitches that could last during the first few weeks of enrolment, which runs through the end of March.
The scheme has been the apple of discord between Obama’s Democratic Party and the Republicans, who questioned whether the 2010 Affordable Care Act will succeed.
"These exchanges are going live today with too many unanswered questions and too many unsolved problems," Orrin Hatch, a Republican senator from Utah said during a speech in the Senate. "The Obama administration should have acknowledged the ample warning signs of problems in the exchanges and heeded the many calls for delay."
It was not clear if the problems signaled overwhelming interest in signing up for insurance, a lack of capacity or connectivity for state or federal systems, or even some kind of intrusion by Obamacare's opponents. New York, for example, reported 7.5 million visitors.
"The level of functionality they're offering today is worse than we might have anticipated. I expected a level where you could at least get to the point of shopping," said Austin Bordelon, an analyst with healthcare consulting group Leavitt Partners, who monitored federal and state marketplaces through the day. "But really, you just can't get through the door."
The Patient Protection and Affordable Care Act, commonly known as Obamacare, will provide subsidised health insurance based on income through the state exchanges and expand Medicaid coverage for the poor from 1 January 2014, representing the most ambitious US social program since Medicare plans for the elderly launched in the 1960s.
Chris Carlin, a 25-year-old student and part-time worker from the Los Angeles area, said he was unable to access health plan details on the California exchange, but would keep trying.
"This is a huge deal for me," he said. "I haven't had health insurance since high school - that's been 7 years."