Outgoing Health and Human Services Secretary Kathleen Sebelius says the timeline for the ObamaCare rollout was "flat-out wrong" and that the federal exchange could have used “more time and testing” before going online.

Sebelius, who led the agency through the problem-plagued rollout, made her comments in an interview that aired Sunday on “NBC’s “Meet the Press,” the first interview since she announced her resignation Thursday.

"Clearly, the estimate that it was ready to go Oct. 1 was just flat-out wrong," she said Sunday.

Sebelius also said the roughly first eight weeks of the glitch-filled rollout was the low point of her five years as secretary.

Still, she defended the President Obama's signature law, arguing millions of Americans now have access to health care because of it.

"People have competitive choices and real information for the first time ever in this insurance market," Sebelius said.

The federal site, HealthCare.gov, was supposed to be the primary place for people to buy private insurance under the 2010 health care law. But its first several weeks were an embarrassment for the administration and its allies.

“I think there's no question -- and I've said this many times -- that the launch of the website was terribly flawed and terribly difficult," Sebelius said.

She also said the president setting a Dec. 1 deadline to have the website repaired was a nerve-racking experience.

"Having failed once at the front of October, the first of December became a critical juncture," Sebelius said. "That was a pretty scary date."

Her resignation comes just a week after sign-ups for insurance coverage ended, enrolling 7.1 million people and exceeding initial expectations. Enrollment has since increased to 7.5 million as people were given extra time to complete applications.

The departing secretary said she decided after the 2012 presidential election that she wanted to leave the administration but decided to stay through the sign-up period. Sebelius said she gave her resignation in March and that Obama did not try to convince her to stay through the end of his term.

“I thought it was fair to either commit until January of 2017 or leave with enough time that he would get a strong, competent leader," Sebelius said. "I made it pretty clear that it really wasn't an option to stay on."

She also said she wished she had the gift of hindsight about the rollout.

"If I had a magic wand and could go back to mid-September and ask different questions based on what I know now," I would, she said. "I thought I was getting the best information from the best experts, but clearly that didn't go well. … "Could we have used more time and testing? You bet."

She acknowledged part of the problem was states deciding whether they would use the federal site or create their own, which she described as a “moving target.”

The Associated Press contributed to this report.