Here are four of the top key moments from Health and Human Services Secretary Kathleen Sebelius's testimony before the House Energy and Commerce Committee Wednesday. (Sarah Parnass/The Washington Post)

New problems emerged Wednesday with the implementation of President Obama’s health-care law even as Health and Human Services Secretary Kathleen Sebelius assured lawmakers that “miserably frustrating” problems with a nearly month-old health-insurance Web site would soon be fixed.

The Web site, HealthCare.gov, was down again most of the morning while Sebelius was testifying before a House committee. And new security issues with the site were raised Wednesday after an internal memo obtained by The Washington Post and other media outlets showed that, days before the Web site’s launch, administration officials knew it put the privacy of user data at risk.

The internal HHS memo warned that the system had not been sufficiently tested, “exposing a level of uncertainty that can be deemed high risk,” although the authors of the memo did not appear to have a specific vulnerability in mind.

Sebelius, testifying Wednesday morning before the House Energy and Commerce Committee, offered assurances that consumers’ personal data were safe.

She acknowledged that “access to HealthCare.gov has been a miserably frustrating experience for way too many Americans,” and she pledged that the problems would be fixed by the end of November. She offered an apology for the site’s troubled launch, while also attributing the breakdowns to private-sector contractors.

A look at the consumer's route through the HealthCare.gov website and the potential failure points.

“I am as frustrated and angry as anyone with the flawed launch of HealthCare.gov,” Sebelius told the committee in an opening statement. Addressing Americans who want to buy health insurance but have been stymied by the Web site, she said: “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.” She said the problems are “fixable.”

The hearing marked Sebelius’s first public appearance before lawmakers to publicly explain the problems with the launch of HealthCare.gov.

According to the Sept. 27 memo to Medicare chief Marilyn Tavenner, a Web site contractor was not able to test all the security controls before the launch. The memo recommended setting up a security team to address risks and conduct daily tests, with a full security test to follow within two to three months.

Questioning Sebelius about the security issue, Rep. Anna G. Eshoo (D-Calif.) cited “a security break that arose recently” and asked Sebelius if she were confident that the new system would “secure the financial information that applicants have to disclose.”

Sebelius said she does have that confidence, adding that “there was not a breach” but a “theoretical problem” raised by a “skilled hacker.” She said the problem “was immediately fixed.”

Committee Republicans were not convinced.

“You accepted a risk on behalf of every person . . . that put their personal and financial information at risk because you did not even have the most basic ‘end-to-end’ test on security of this system,” Rep. Mike Rogers (R-Mich.) told Sebelius. “Amazon would never do this. ProFlowers would never do this. Kayak would never do this.”

Secretary of Health and Human Services Kathleen Sebelius said at a congressional hearing Wednesday that the clause determining if Americans could keep their old insurance plan under Obamacare did not change. (The Washington Post)

In opening the hearing, Rep. Fred Upton (R-Mich.), the committee chairman, said, “This is more than a Web site problem. . . . Malfunctions have become the norm.” He said that “Americans are scared and frustrated, and this situation should rise above politics.”

Rep. Henry A. Waxman (Calif.), the top Democrat on the committee, used his opening statement to tout the benefits of the health-care law, officially called the Affordable Care Act but widely known as Obamacare. “The Affordable Care Act is working,” he said. “I would urge my colleagues to stop hyperventilating,” he added, saying the problems would be fixed.

Under questioning from committee Republicans during the 3 1/2-hour hearing, Sebelius disputed contentions that people are losing health insurance under the new law. If people get notices of cancellation because their existing insurance was not grandfathered in and does not meet minimum standards, “it’s the law that they must get another plan,” Sebelius said. “Continuing coverage is part of the law, and that wasn’t the case in the past.”

In one testy exchange with Rep. Marsha Blackburn (R-Tenn.) about the Web site’s problems, Sebelius said: “Hold me accountable for the debacle. I’m responsible.”

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“I desperately want to get it fixed,” she said at another point in the hearing. “The only thing that builds the public’s confidence back is fixing it.”

As it happened, HealthCare.gov was down for most of the morning while the HHS secretary was testifying.

Sebelius said in response to questions that the government so far has spent $118 million on the Web site and $56 million on other information technology to support the Web site. She said she was confident that the site would be “optimally functioning” by the end of November.

She also was questioned about contractors’ statements that they needed months to conduct end-to-end testing on the system, rather than the two weeks or less they were given.

“Certainly . . . we did not adequately do end-to-end testing,” Sebelius said. “The products were not locked and loaded into the system until the third week of September.”

She explained later in the hearing that one reason HealthCare.gov could not be tested sooner was that it had to be loaded with price and other data from insurers. Officials did not have all that information until September, she said.

Nearly 700,000 applications have been submitted to federal and state insurance exchanges since the Web site was launched Oct. 1, and more than 20 million unique visits to the site confirm that Americans are looking for quality, affordable coverage, Sebelius said in separate written testimony submitted to the committee in advance of the hearing.

“Unfortunately, the experience on HealthCare.gov has been frustrating for many Americans,” she said. “The initial consumer experience of HealthCare.gov has not lived up to the expectations of the American people and is not acceptable. We are committed to fixing these problems as soon as possible.”

Sebelius said “private sector contractors” were hired to build the insurance marketplace. “Unfortunately, a subset of those contracts for HealthCare.gov have not met expectations. Among other issues, the initial wave of interest stressed the account service, resulting in many consumers experiencing difficulty signing up, while those who were able to sign up sometimes had problems logging in.”

She cited “a number of improvements” in response to the problems, including site updates and bug fixes. She said in her written testimony: “Today, more individuals are successfully creating accounts, logging in, and moving on to apply for coverage and shop for plans. We are pleased with these quick improvements, but we know there is still significant, additional work to be done.”

Sebelius made no reference in her prepared remarks to a controversy over canceled health insurance policies, with hundreds of thousands of Americans receiving notices that their insurance is being canceled as of Dec. 31.

But the subject came up often in questions to the former Kansas governor. Prodded by committee Republicans, Sebelius denied that President Obama had misled Americans by pledging that they could keep health-insurance plans they liked under the new health-care law. She said some people in the individual insurance market are receiving cancellation notices because the policies were issued after the law was enacted and do not meet basic requirements.

Seeking to put the cancellation issue in context, Sebelius said that 95 percent of people who have health insurance get it through their employers or a federal program such as Medicare. The rest, about 5 percent, are in the individual market. A portion of them, about 12 million people, have a plan that does not cover the basic benefits required under the health-care law and cannot be grandfathered in, which means their plans will be discontinued this year.

Of those, about half will be eligible for federal subsidies to help them afford coverage on the insurance exchanges, she said.

Before the new law reformed it, “the individual insurance market was dysfunctional,” she said, noting that policies could be canceled because of preexisting conditions or other issues, to the disadvantage of consumers. “This market has always been the Wild West,” she said.

As Sebelius answered questions, the hearing see-sawed between supportive and contentious, with Republican lawmakers hammering her with stories of constituents whose plans are being canceled and sarcastic jibes about the Web site, and Democrats praising the intent of the health-care law and providing examples of constituents who have benefited.

At one point, Rep. Michael Burgess (R-Tex.) reminded Sebelius of the many government officials who had testified in advance of the rollout and predicted that HealthCare.gov would work. “Were they being purposely misleading or are they really not that smart?” he asked. Without waiting for an answer, the congressman then asked Sebelius if she would fire Gary Cohen, the head of the Center for Consumer Information and Insurance Oversight in the Centers for Medicare and Medicaid Services, a division of HHS. Cohen in many ways was the face of the IT effort behind HealthCare.gov.

“Will you ask for the resignation of Gary Cohen because he has repeatedly come before this committee and he has misled us?” Burgess said.

“I will not,” came Sebelius’s clipped reply.

Rep. Frank Pallone Jr. (D-N.J.) came to Sebelius’s defense, charging that Republicans were out to “sabotage the Affordable Care Act, scare people and bring up red herrings.” He told the committee: “This whole idea . . . that somehow policies are being canceled and people don’t have alternatives is just another red herring. This is not socialized medicine. This is private insurance in a competitive market.” He added that “insurance companies are canceling lousy policies with high prices,” in part because they can no longer compete with better plans.

Rep. Eliot Engel (D-N.Y.) also criticized Republican lawmakers, saying they reminded him of Chicken Little. But “unlike Chicken Little, my Republican colleagues are actually rooting for the sky to fall,” he said. “They’re rooting for failure.”

Rep. Cory Gardner (R-Colo.) told Sebelius that he and his family buy their health insurance on the private market and, like many other people, received notification that their plan is being discontinued. He said he chose to reject his congressional insurance to be more like people in his district.

“Why aren’t you losing your insurance?” he demanded of Sebelius. “Why won’t you go into this exchange?”

Sebelius responded that she is not eligible, because people who get affordable coverage through their employers may not apply through the marketplace.

“I would urge you to be like the American people,” Gardner said, before asking for a waiver from the health-care law for his Colorado district.

Rep. Billy Long (R-Mo.) also pressed Sebelius to say whether she would be willing to “forgo” her insurance as a federal official and enter the exchanges.

Waxman, the California Democrat, interjected that if she were legally able to do what Long suggested, Sebelius should try to find a policy “that protects you from cheap shots.”

Sebelius said, “I would gladly join the exchange if I didn’t have affordable coverage in my workplace.”

Under questioning by Rep. Joe Pitts (R-Tex.), Sebelius offered some insight into the decision not to include a “window-shopping” feature when HealthCare.gov launched. This would have let people browse possible rates and plans before they created an account. Since the option was not available, people had to create an account before viewing their possible rates.

Technology experts have said that if the feature had been included, it would have taken pressure off other parts of the site and prevented some of the problems that caused the system to fail. But Republicans allege that the decision was made to hide rates from consumers.

Last week, CGI Federal, the main contractor in charge of the project, said an agency within Sebelius’s department made the decision to “turn off” the browsing tool, even though it was ready.

Sebelius said Wednesday that Tavenner, administrator of the Centers for Medicare and Medicaid Services, made the decision to leave out that function. She said officials were trying to “pare back” the site to ensure that it did not get bogged down by a lot of extraneous tools.

“We were anxious to get the Web site up and running and functional, which we clearly have failed to do,” she said.

In response to other questions, Sebelius firmly pushed back on demands to release information about how many people have successfully enrolled in health insurance since the state and federal marketplaces launched. She said it was impossible to know for sure because of the technological problems afflicting the enrollment system.

“The numbers are not reliable,” Sebelius said.

Asked if she would let that information be disseminated by the contractors, who said last week they are not permitted by their contracts with the administration to release those data, she said she would not.

“I don’t want to turn over anything that is not confirmed and reliable,” she said. “According to the insurance companies who are eager to enroll people, they are not getting reliable data. . . . The system isn’t functioning, so we aren’t getting that reliable data.”

Tavenner, in testimony Tuesday before the House Ways and Means Committee, said numbers on enrollees would not be available until mid-November. “We expect the initial number to be small,” she said.

Speaking to reporters Wednesday on Capitol Hill, House Minority Leader Nancy Pelosi (D-Calif.) declined to cast blame for the botched rollout of HealthCare.gov, saying the focus instead should be on fixing the problems and moving on.

Asked whether she thinks some person or entity should be held responsible, Pelosi said: “It doesn’t matter. It matters that it gets fixed.”

But citing recent news reports, Pelosi suggested that contractor CGI Federal had been less than truthful in its public and private assessments of the Web site.

She added that “a fresh set of eyes” besides Congress should be tasked with investigating the situation and assessing blame. But she declined to say who should conduct a study.

Debbi Wilgoren and Ed O’Keefe contributed to this report.