Kathleen Sebelius has resigned as Secretary of Health and Human Services, a White House official confirmed.
Sebelius' resignation comes just one week after the enrollment period for health plans under the Affordable Care Act came to a close, a rollout marred by disastrous early technical glitches.
President Barack Obama will announce the move on Friday. He will also nominate White House Office of Management and Budget Director Sylvia Mathews Burwell on Friday to replace Sebelius, the White House official said.
The move sets the stage for a contentious election-year battle over Burwell's confirmation.
"The president wants to make sure we have a proven manager and relentless implementer in the job over there, which is why he is going to nominate Sylvia," Denis R. McDonough, White House chief of staff, told The New York Times.
Burwell has been overseeing White House OMB for just under a year, having served previously as president of the Walmart Foundation. She is a key player inside the White House on all budget matters, and she served as one of Obama's closest advisers during the federal government shutdown last year. She's a graduate of Harvard and Oxford University, and an alumnus of the Clinton administration.
Sebelius notified Obama of her decision in early March, according to the White House official.
"Secretary Sebelius told the President that she felt confident in the trajectory for enrollment and implementation of the Affordable Care Act, and that she believed that once open enrollment ended it would be the right time to transition the Department to new leadership," the official said.
Enrollment in health insurance exchanges established by the Affordable Care Act has grown to 7.5 million Americans, up from 7.1 million last week, Sebelius told a congressional panel on Thursday. Despite the disastrous rollout, enrollment ended up meeting and even exceeding some original expectations.
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