WASHINGTON, D.C. — President Barack Obama is nominating Marilyn Tavenner to succeed Donald M. Berwick as administrator of the Centers for Medicare and Medicaid Services.

Tavenner, who is the agency’s principal deputy administrator, will serve on an acting basis as administrator during the confirmation process, according to an announcement to CMS staff.

Berwick was not confirmed by the Senate and instead got a recess appointment from Obama. His appointment expires Dec. 31 and he will be stepping down Dec. 2.

A nurse, Tavenner has has played a key role in overseeing Medicare, Medicaid and the Children's Health Insurance Program. In remarks to the National Association of Medicaid Directors last month, Tavenner shared her thoughts on how to control health care costs, themes that are very similar to ideas Berwick has expressed repeatedly throughout his tenure.

"The only way to stabilize costs without cutting benefits or provider fees is to improve care to those with the highest health care costs," she said. Tavenner also said she opposed Republican efforts to turn Medicaid into a block grant that would limit the amount of federal funding states can receive for the program. "That approach would simply dump the problem on states and force them to dump patients, benefits or make provider cuts or all the above," she said.

Before coming to CMS, Tavenner served as secretary of Virginia’s Health and Human Services where she oversaw 12 agencies that employed 18,000 people. Her career also included 25 years working for the Hospital Corporation of America where she started as a staff nurse and became president of outpatient services, according to an alumni profile posted on the Virginia Commonwealth University’s web site.

Deep partisan divides have stopped Congress from confirming Berwick since mid-October 2006, creating instability in the agency that oversees the Medicare and Medicaid programs. Obama installed Berwick in July 2010 as a recess appointment, which was heavily criticized by Republicans who accused the pediatrician of favoring health care rationing -- a charge Democrats dismissed as nonsense.

The current political climate on Capitol Hill may mean that Tavenner is just as likely to see her nomination stall. A bipartisan panel charged with finding $1.2 trillion in budget savings over the next decade deadlocked with members unable to bridge differences over the difficult issues of taxes and entitlement spending and rancor between the parties is only expected to grow heading into the 2012 elections.

—Staff writers Sarah Barr and Christian Torres contributed to this article.