The Obama administration official who oversaw the botched rollout of the "Obamacare" website, Healthcare.gov, announced Friday she will resign as head of the agency that also manages the Medicare and Medicaid health care programs.

"It is with sadness and mixed emotions that I write to tell you that February will be my last month," Marilyn Tavenner, administrator for the Centers for Medicare and Medicaid Services (CMS), said in an email to staff.

She gave no reason in the email for her departure.