US President Barack Obama's embattled health secretary has apologised to the American people over the botched rollout of his healthcare law's insurance marketplace websites.
Kathleen Sebelius was questioned by a House panel about the 1 October launch.
"You deserve better," Ms Sebelius said to the public, pledging the site would be repaired by the end of November.
The federal and state-run websites had been projected to enrol seven million uninsured Americans in the first year.
"I'm accountable to you for fixing these problems and I'm committed to earning your confidence back," Ms Sebelius said in sworn testimony in the House energy and commerce committee.
'Improving health security'
The 1 October launch of the federal and state marketplace websites was the culmination of more than three years of political combat in Washington over the Patient Protection and Affordable Care Act, signed into law by Mr Obama in 2010 and known to both sides as Obamacare.
Considered the largest overhaul of the US healthcare system since the 1960s, it aims to extend health insurance coverage to the estimated 15% of the US population who lack it. Those people receive no coverage from their employers and are not covered by US health programmes for the poor and the elderly.
But Healthcare.gov - akin to a shopping website for health insurance plans - has been plagued by glitches, especially long wait times to sign up and serious flaws on the back end where customers' data are processed and sent to insurance companies.
Ms Sebelius, appointed secretary of health and human services by Mr Obama in 2009, told the House committee in prepared remarks that more than 20 million people had visited the website since its launch, but acknowledged the experience was "frustrating" for many Americans.
The Obama administration has declined to say how many Americans have actually enrolled in new policies through the sites, rankling Republicans who accuse it of withholding vital information.
Ms Sebelius said the problems were "fixable" and that changes had already been made to improve the site's speed and reliability. She said the federal government was working with the numerous contractors who built the site, and that the Obama administration projected it would be fully up and running by the end of November.
The committee's senior Democrat, Henry Waxman, acknowledged "the launch of the new website has not gone well" but just as with a prescription drug programme for pensioners enacted under Republican President George Bush, the "early glitches will soon be forgotten".
"We should keep this issue in perspective - the Affordable Care Act is working," he said. "It has been improving the health security of millions of Americans for the past three years."
Republican committee chairman Fred Upton called the website "inept", saying that five weeks into enrolment, "the news seems to get worse by the day".
He also questioned why hundreds of thousands of Americans had received letters from their insurance companies saying their policies were being cancelled - despite past assurances from Mr Obama that people who liked their insurance plans would be able to keep them under the health law.
Ms Sebelius rejected that criticism, saying that people whose plans were dropped would have access under the new law to better insurance coverage at comparable rates.
And Democrat Frank Pallone, a supporter of the health law, called Republicans' concerns over the cancellation letters a "red herring" and said insurance companies were closing "lousy policies with high prices because they can't compete".
Some Republicans have called for Ms Sebelius' resignation over the issue.
They argue the problems with the website that prevent consumers from signing up reflect broader problems with the healthcare law.
Republicans view the health law as a costly and inappropriate government intrusion into the healthcare system, and have sought to undo or undermine it at every turn.
"Hold me accountable for the debacle. I'm responsible," Ms Sebelius told the committee after several members asked which contractors and Obama administration officials were responsible for issues.
Aside from establishing the healthcare.gov health insurance marketplace website and others run by the states, the law bolsters coverage requirements for insurance firms, mandates that individuals carry insurance or pay a tax penalty, and offers subsidies to assist in the purchase of the insurance. It also expands eligibility for the Medicaid government health programme for the poor.
Amid the fallout, the White House has said it will grant a six-week extension - until 31 March 2014 - in the healthcare law's requirement for individuals to buy insurance or face a tax penalty.
Mr Obama is scheduled to speak about the healthcare rollout in the state of Massachusetts on Wednesday afternoon.