President Obama offered an impassioned defense of the Affordable Care Act on Monday, acknowledging the technical failures of the Health Care.gov Web site, but providing little new information about the problems with the online portal or the efforts by government contractors to fix it.

With Republican critics seizing on the Web site’s issues as evidence of deeper flaws in the health care law, Mr. Obama sought to deflect attention from the continuing problems by focusing on ways to get coverage without going online. Like a TV pitchman, the president urged viewers to call the government’s toll–free number for health insurance, acknowledging that "the wait times probably might go up a little bit now."

In remarks in the Rose Garden, Mr. Obama acknowledged serious technical issues with the Web site, declaring that "no one is madder than me." He offered no new information about how many people have managed to enroll since the online exchanges opened on Oct. 1. And he did not address questions about who, if anyone, might be held responsible for the failure.

The president and his top aides played down the importance of the online marketplace that his administration once heralded as the key to the law’s success. Mr. Obama promised that officials are working to fix the Web site, but said that Republican critics should "stop rooting" for the failure of a law that provides health insurance to people who do not have it.

"We did not wage this long and contentious battle just around a Web site," Mr. Obama told supporters. "That’s not what this was about. We waged this battle to make sure that millions of Americans in the wealthiest nation on earth finally have the same chance to get the same security of affordable, quality health care as anybody else."

Speaker John A. Boehner said in a statement after the president’s event that the administration is "not prepared to be straight" with the American people about the issues involving the health care Web site and the insurance program behind it.

"Every day, new questions about the president’s health care law arise, but candid explanations are nowhere to be found," said Mr. Boehner, of Ohio. "This decision continues a troubling pattern of this administration seeking to avoid accountability and stonewall the public."

As they have pushed to repeal or defund Mr. Obama’s signature health care law, Republicans have demanded that the administration provide data to show how many — or how few — people have enrolled in health insurance plans through the online portal. On Monday, White House officials again refused, saying they plan to offer such numbers in mid–November and monthly after that.

The White House refusal to provide enrollment data stands in contrast to the administration’s insistence that states submit detailed weekly reports on the number and characteristics of people who sign up for insurance through state–run exchanges. The Department of Health and Human Services said it needed the data so it could "track those measures which have the most potential to adversely impact beneficiaries related to their ability to enroll in insurance plans."

The department said it wanted to shine a spotlight on the performance of state exchanges, which were built with the help of federal money, and it emphasized the importance of "transparency in the performance of marketplaces."

Moreover, the administration said that frequent reporting of performance data was needed so federal officials could spot problems with the state exchanges and step in to help fix them. In fact, the state exchanges have generally performed better than the federal exchange.

With many consumers still unable to use the online portal, health policy experts outside the government have begun discussing possible ways to provide relief if the problem continues.

One option is to extend the six–month enrollment period, which is set to end on March 31. Another is to exempt some people from the tax penalties that apply to those who go without insurance in 2014.

Jay Carney, the White House press secretary, suggested that such relief would be unnecessary if the administration fixed the Web site so people could enroll easily in the near future.

Over the weekend, the administration announced a "tech surge" that would bring in "the best and the brightest from both inside and outside government" to fix the Web site. But on Monday, White House officials declined to answer questions about the contractors who designed HealthCare.gov or to provide the names of the "experts from some of America’s top private–sector tech companies" that the president said have offered to help the government fix the site.

The White House also declined to comment on a decision by Kathleen Sebelius, the secretary of health and human services, not to testify on Thursday at a hearing by the House Energy and Commerce Committee. Ms. Sebelius has said she will be at a mental health gala at the John F. Kennedy Presidential Library and Museum in Boston that day.

"For specifics about, you know, requests to individual departments and officials who will be made available, I’d refer you to those departments," Mr. Carney said. Department of Health and Human Services officials said Ms. Sebelius would make herself available to testify before Congress next week, but Republicans said that was not good enough.

"What is more important to Secretary Sebelius than providing answers to the American people?" Mr. Boehner asked.

Late Monday, the committee reached an agreement with Ms. Sebelius to have her answer questions before the panel on Wednesday, Oct. 30, according to a news released posted to the committee’s Web site.

For months, federal health officials had promoted the Web site of the federal exchange as the best place for consumers to compare and buy health insurance plans and obtain financial assistance to help pay premiums. But on Monday, with many users still frustrated by technical problems on the Web site, Mr. Obama emphasized that consumers could also apply for insurance over the phone by calling 800–318–2596.

The home page of the Web site for the federal exchange used to have a single button that said, "Apply now," which began an online application process. The Web site now displays two buttons: "Apply online" and "Apply by phone."

That message is a turnabout for the administration, which had spent months leading up to the Oct. 1 opening of the marketplaces by saying it would focus on tech–savvy young people.

For the insurance marketplaces to work effectively, they must attract healthy, young people as well as older, sicker people. Officials had assumed that older, uninsured people would be eager to sign up, so the administration developed elaborate plans to woo the younger ones.

Those plans were largely built around getting young people to sign on to the Web site, which Mr. Obama had said would be as easy to use as Amazon.com or other consumer–oriented Web sites. In his remarks on Monday, Mr. Obama made clear that those efforts will have to wait until the Internet portal is working more effectively. He urged young people to be patient and to return to the Web site in the weeks and months ahead.

"Unlike the day after Thanksgiving sales for the latest PlayStation or flat–screen TVs, the insurance plans don’t run out," Mr. Obama said. "They’re not going to sell out. They’ll be available through the marketplace throughout the open enrollment period. The prices that insurers have set will not change. So everybody who wants insurance through the marketplace will get insurance, period."