WASHINGTON -- In her first appearance before Congress since the botched debut of the federal health-care website, Health and Human Services Secretary Kathleen Sebelius on Wednesday apologized for the "debacle," accepted responsibility and promised the technical problems could be fixed.

Sebelius acknowledged that enrolling in insurance plans through the federal government's online marketplace was a "miserably frustrating experience for way too many Americans" -- an observation Republicans repeatedly underscored by pointing to a screen that showed in real time that the website, healthcare.gov, had gone down.

"I am as frustrated and angry as anyone with the flawed launch," she told the House Energy and Commerce Committee, becoming the second administration official to testify before Congress on the issue. "So let me say directly to these Americans, you deserve better. I apologize. I'm accountable to you for fixing these problems. And I'm committed to earning your confidence back by fixing the site."

In 3 + hours of testimony, Sebelius endured an intense grilling from Republican critics, but tried to spotlight what she argued were the overlooked successes of the health care law.

"Millions of Americans are clearly eager to learn about their options and to finally achieve health care security made possible by the Affordable Care Act," she said. "And my commitment is to deliver on that promise."

Sebelius, a popular second-term Kansas governor when President Barack Obama tapped her to run the department and oversee his planned health care overhaul, is in the eye of a maelstrom that has undermined confidence in the administration and given new ammunition to GOP critics of his biggest domestic achievement.

"Americans were assured that their experience would be similar to other online transactions, like purchasing a flight or ordering a pizza," said committee Chairman Fred Upton, R-Mich. "But after more than three years to prepare, malfunctions have become the norm."

The administration has promised that the web site will be fixed by the end of November. Upton said Sebelius had agreed to testify again in the first week of December.

Republicans have sought to pin the blame for the web site's dismal performance on Sebelius. Last week, 32 members of the House signed a letter to Obama urging him to fire her as a "powerful signal that the American people will not be held responsible for her department's failings." This week, the top Republican on the Senate Health Committee, Lamar Alexander, R-Tenn., also said Sebelius should step down.

Senior White House officials have dismissed such calls, saying their priority was to fix the problems. A White House spokesman reiterated Wednesday that the president "has complete confidence" in Sebelius.

Sebelius also said she did not support delaying a tax penalty for Americans who did not have health insurance next year, as many lawmakers, including Democrats, have called for. "We're still at the beginning of a six-month open enrollment, which extends through the end of March. And there's plenty of time to sign up," she said.

The technical problems that have marred the rollout of a crucial feature of the health care law were a recurring theme of the House hearing. But Sebelius argued that, despite major issues, the web site had never crashed. "It is functional, but at a very slow speed and very low reliability," she said.

Republicans also continued a new line of attack over Obama's promise that Americans who already had health insurance would be able to keep their policies if they liked them.

"I'd call this a red herring that misled voters, intentional or not," Rep. Phil Gingrey, R-Ga., said. "Your words and those of the president, as he campaigned last year ... seem to be directly refuted by the millions of cancellation notices already sent to Americans just in the past few weeks."

Sebelius told the committee the administration lacked "reliable data" on how many Americans had enrolled in new plans so far. She speculated that, because of the "flawed launch," it probably would be "a very small number."

Insurance companies have reported receiving inadequate or confusing information, which Sebelius said was one of the "priority fixes" now being made. Sebelius said she intended to release "confirmed data" on a monthly basis beginning next month. "The system isn't functioning, so we are not getting that reliable data," she said.

Critics have suspected that the administration was withholding information about enrollment because the numbers were low. If signups are significantly below expectations it could jeopardize the health care law, particularly if younger, healthier Americans do not enroll to help balance older, sicker ones who do.

Rep. Mike Rogers, R-Mich., who chairs the House Intelligence Committee, also raised concerns about the security of the personal data consumers submit to the web site. He cited warnings in a Sept. 27 memo from Marilyn Tavenner, administrator of the federal Centers for Medicare and Medicaid Services, which oversees the online health marketplace. Tavenner noted that an outside contractor had not been able to test security controls.

"Don't you think you had the obligation to tell the American people that we're going to put you in this system, but beware, your information is likely to be vulnerable?" Rogers asked.

Sebelius said regular monitoring and testing continued, and security protocols were being upgraded.

When Obama introduced Sebelius as his nominee in 2009, he said of the former governor and state insurance commissioner, "I know she will bring some much-needed grace and good humor to Washington."

That was tested at Wednesday's hearing as Sebelius faced sometimes hostile inquiries from Republican lawmakers.

"Madam Secretary, while you're from Kansas, we're not in Kansas anymore," Rep. Joe L. Barton, R-Texas, said to Sebelius. "Some might say that we are actually in 'The Wizard of Oz' land, given the parallel universes we appear to be habitating."

In one exchange, a Mississippi Republican repeatedly pressed Sebelius over whether the president, and not she, should be held responsible for the failures of healthcare.gov.

"I think it's great that you're a team player and you're taking responsibility. It is the president's ultimate responsibility, correct?" asked Rep. Gregg Harper.

"You clearly - " an increasingly frustrated Sebelius began, before stopping herself. "Whatever. Yes, he is the president. He is responsible for government programs."

Later, she tangled with Rep. Billy Long, R-Mo., over why she would not enroll in an insurance plan through the exchange. She repeatedly explained she could not because she already had coverage as a federal employee.

"I would gladly join the exchange, if I didn't have affordable coverage in my workplace," she finally said.

Democratic members of the committee sought to deflect some of the fire aimed at Sebelius. Rep. Henry A. Waxman, D-Calif., joked she needed an insurance policy that "would protect you from cheap shots."

Sebelius appeared to emerge largely unscathed at the end of the hearing, with even one of the top Republican critics of the Affordable Care Act declining to join calls for her to step down.

"This doesn't end with her. This is President Obama's signature law," said Rep. Steve Scalise, R-La., chairman of the Republican Study Committee, an influential group of conservatives. "The main thing I wanted is for Secretary Sebelius to hear the stories of real American people who are being hurt by this law."

(c) 2013 McClatchy News Service