Health and Human Services Secretary Kathleen Sebelius says officials are working "24-7" to make the government's health insurance website better.
Sebelius was in Phoenix on Thursday amid calls for her resignation after the clunky rollout of online insurance exchanges under President Barack Obama's health care law.
INTERACTIVE: Health Care Website Issues
She says most of the people wanting her to step down "do not want this program to work in the first place."
The former Kansas governor is the Obama administration's public point person on the law's implementation.
Sebelius says nobody has been fired over technical glitches and a lot of the problems were caused by a surge in demand.
While Sebelius was in Phoenix, she toured a Health and Human Services call center and spoke with "navigators" who have been trained to educate people about enrolling for coverage.
U.S. Sen. Mark Begich says trying to access the online health insurance marketplace during the first week of its rollout was a "disaster."
But he says he's seen improvements in the site over the last few days. And he dismissed any suggestions that the law should be dumped because of problems with the website.
Alaska's junior senator has joined with several Democratic colleagues in seeking a longer open enrollment period for individuals to buy health insurance under the new federal health care law.
Begich tells The Associated Press he doesn't believe there should be a delay of, say, a year. Rather, he says it should match however long it takes for the website to be properly functioning. He says if that's a month, open enrollment should be extended a month.