Robert Pear / New York Times News Service

WASHINGTON — Kathleen Sebelius, the secretary of health and human services, said Wednesday that the government needed to fix hundreds of problems with the website for the federal health insurance marketplace, but she rejected bipartisan calls to delay parts of the new health care law.

She made her comments at a hearing of the Senate Finance Committee just hours after the Obama administration had disclosed that the chief information officer at the Centers for Medicare and Medicaid Services would retire. His office supervised the creation of the troubled website.

Even as Sebelius testified about progress in repairing the website, agency officials were reporting new problems Wednesday.

“The site is performing slowly,” said Julie Bataille, a spokeswoman for the Centers for Medicare and Medicaid Services. “Some users have difficulty logging in and receive error messages.”

Bataille said it was hard to pinpoint the cause, because different consumers had experienced different problems. Some people who have created password-protected accounts have said that they cannot get into their accounts to shop for insurance. Under the new health care law, most Americans will be required to have coverage next year.

The online marketplace, or exchange, has been plagued with problems since it opened Oct. 1.

Sebelius said officials had a list of “a couple of hundred functional fixes” that had to be made so the website,, would work smoothly for most users by Nov. 30, a deadline set by the administration.

“We’re not where we need to be,” Sebelius said. “It’s a pretty aggressive schedule to get to the entire punch list by the end of November.”

With many people unable to obtain coverage through the website, lawmakers in both parties have suggested extending the open enrollment period or delaying the financial penalties for people who go without insurance. Sebelius refused to consider those proposals.

“Delaying the Affordable Care Act would not delay people’s cancer or diabetes or Parkinson’s disease,” she said. “It would not delay the need for mental health services or cholesterol screenings or prenatal care.”

“For millions of Americans, delay is not an option,” Sebelius said. “People’s lives depend on this.”

Sebelius said she was accountable for what she described as “a miserable five weeks” and the “excruciatingly awful” debut of the insurance website.