US President Barack Obama sought on Monday to limit political damage from the problematic launch of the government website for his signature healthcare law as Washington became embroiled in a new uproar days after a debt default was narrowly averted.

With many Americans experiencing error messages and long waits in trying to sign on to healthcare.gov, Republicans in Congress who have fought the Affordable Care Act since before its 2010 passage renewed calls for a delay in the rollout of the law in order to fix it.

Obama surrounded himself in the White House Rose Garden with a group of people who have successfully navigated the system. In a speech, Obama declared himself frustrated with the technical glitches and vowed to get them repaired.

"Nobody's madder than me about the fact that the website isn't working as well as it should, which means it's going to get fixed," said Obama, who counts the law as his most significant domestic policy achievement.

Online insurance exchanges were launched on October 1 under the law, often called "Obamacare," to offer health insurance plans to millions of uninsured Americans. But many people trying to shop for health insurance at healthcare.gov have failed to make it through the system despite repeated tries.

Republicans also renewed their demand that Obama's top health adviser, Health and Human Services Secretary Kathleen Sebelius, testify this week before a House of Representatives oversight hearing about the website's problems.

"Americans didn't get any answers from the president today, but the House's oversight of this failure is just beginning," said House Speaker John Boehner, the top Republican in Congress.

A Sebelius spokeswoman said the HHS secretary would testify next week - not this week - due to a scheduling conflict.

"We are in close communication with the committee and have expressed our desire to be responsive to their request," Sebelius spokeswoman Joanne Peters said.

The White House said last week that Obama still has "full confidence" in Sebelius, whose department is responsible for implementing the law.

For Republicans, the website's woes offered them a new battlefront to fight what they feel is Obama's unwarranted expansion of the federal government. Last week, they were forced to back down from a budget fight begun by their bid to cut off funding for the healthcare law - a squabble that led to a 16-day government shutdown and a close call with a debt default.

'It's not working'

Senate Republican Leader Mitch McConnell, a central player in settling last week's fiscal impasse, said the healthcare law's problems intensify the need to delay the requirement that every American possess health insurance by March 31 or pay a penalty fee.

"Another campaign-style event won't solve the myriad problems facing consumers under Obamacare," McConnell said. "Obamacare costs too much and it's not working the way they promised. ... It's time for the president to consider delaying this rushed effort."

White House spokesman Jay Carney indicated the administration might have flexibility about the penalty fees because of the site's problems.

HHS said it would issue "guidance" on possible changes regarding the penalty fees at a later date and, echoing comments by Carney, said there was a "disconnect" there that needed to be addressed.

The Affordable Care Act is expected to provide health coverage to an estimated 7 million uninsured Americans through the new online marketplaces that opened for enrollment in all 50 states on October 1.

In the weeks since October 1, many people have encountered a series of bewildering problems such as error messages, garbled text and delays loading pages on the website, which is the administration's online portal for consumers in 36 states.

Obama said the healthcare law was "not just a website," a phrase repeated later by Carney, and urged people having trouble signing up to use the telephone, offering a toll-free number - 800-318-2596 - as an alternative. He said those having problems will be contacted personally.

"There's no sugarcoating it. 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 is more frustrated by that than I am," Obama said.

The administration has said that volume far exceeded expectations, placing a huge burden on the website. Private sector experts are being brought in to help iron out the glitches in the system, officials said.