President Barack Obama has acknowledged widespread technical issues that have plagued the rollout of a major element of his 2010 healthcare law.
In a Rose Garden press conference on Monday, Mr Obama said that despite that its problems, the website was delivering affordable coverage.
Those attempting to sign up for health insurance have reported persistent issues since the 1 October rollout.
US health officials have ordered a “tech surge” to fix the site.
The website’s issues have been overshadowed by the recent partial government shutdown, in which Republican lawmakers attempted to gut the law through US budgetary brinkmanship.
‘It’s really good’
Mr Obama conceded that healthcare.gov “hasn’t worked as smoothly as it was supposed to work”.
“The number of people who’ve visited the site has been overwhelming, which has aggravated some of these underlying problems.”
Mr Obama added: “There’s no sugar coating – the website has been too slow, people have been getting stuck during the application process, and I think it’s fair to say that nobody’s more frustrated by that than I am.
“And there’s no excuse for the problems,” he added, “and these problems are getting fixed.”
He said that notwithstanding the website’s problems, there was “massive demand” and the homepage had been visited nearly 20 million times.
“Precisely because the product is good, I want the cash registers to work, I want the checkout lines to be smooth,” said Mr Obama. “And there’s no excuse for the problems, and these problems are getting fixed.”
He was joined at Monday’s event by people who have successfully enrolled during the first three weeks, include the first person to enrol in the US state of Delaware.
The website is supposed to serve as a clearinghouse for uninsured Americans searching for medical coverage on exchanges set up by the law.
The site serves both as a check to see if applications qualify for government subsidies for the cost of private insurance, as well as being the first enrolment step for specific plans.
It is hoped the exchanges will be the gateway for covering an estimated seven million Americans without health insurance.
The White House has said almost half a million people have applied for healthcare through both federal and state-run exchanges since 1 October.
Exchanges run by individual states do not appear to have been plagued to the same extent by technical problems.
White House officials initially blamed the gremlins on heavy interest in the site, but they recently conceded the flaws were larger and involved software and system design issues.
“I think that there’s no-one more frustrated than the president at the difficulty in the website,” Treasury Secretary Jack Lew told broadcaster NBC on Sunday.
The Department of Health and Human Services, which runs the exchanges, said in a blog post it had already begun to make improvements.
“We know there’s still more work to be done,” the statement said, adding “our team is bringing in some of the best and brightest from both inside and outside government” to fix the ongoing issues.
But the administration has offered few details on who was being brought in from outside the government and the specific causes of the ongoing glitches.
Passed in 2010, the Affordable Care Act, commonly known as Obamacare, has rolled out in multiple steps, including coverage requirements on insurance companies and future tax penalties for those who remain uninsured.
Republicans in Congress have repeatedly attempted to repeal or remove funding from the law, most recently during a 16-day government shutdown which ended with no major concessions from Mr Obama.
Health Secretary Kathleen Sebelius has also been criticised by Republican lawmakers for declining an invitation to testify about the glitches on 24 October.