Donald Berwick, the Medicare administrator who is President Barrack Obama's point man for healthcare reform, has quit after only 17 months in the job.

Berwick, a long-time advocate of patient safety, is resigning as administrator of the Centers for Medicare and Medicaid Services (CMS), effective Dec. 2, The Associated Press reports, citing the White House.

According to the AP, Berwick — "a Harvard professor widely respected for his ideas on how to improve the health care system" — is stepping down after Republicans blocked his confirmation in the Senate.

They have branded the pediatrician an advocate of health care rationing, a claim Berwick denies, "countering that the best way to cut costs is to improve the quality of care," according to Medscape.

The Wall Street Journal reported that:

Berwick's statements as an academic praising Britain's government-run health care had become a source of controversy in politically polarized Washington. Although he later told Congress that "the American system needs its own solution" and Britain's shouldn't be copied here, his critics were not swayed.

Berwick had been running the CMS under a temporary appointment, set to expire at the end of 2011.

He oversaw the early stages of the health care overhaul, which involves significant change to the Medicare and Medicaid health programs, last year.

In June, Berwick presented a report showing that more than 5 million Americans with Medicare took advantage of one or more recommended free preventive medical benefits made available by the Affordable Care Act.

Preventive care services include "wellness" visits, bone mass measurements and cardiovascular, colorectal cancer and diabetes screenings.

White House deputy press secretary Jamie Smith criticized Republicans for "putting political interests above the best interests of the American people," the AP reports

Berwick wrote of "bittersweet emotions" in an email to his staff.

"Our work has been challenging, and the journey is not complete, but we are now well on our way to achieving a whole new level of security and quality for health care in America, helping not just the millions of Americans affected directly by our programs, but truly health care as a whole in our nation," the email read, according to the AP.

Obama will nominate as Berwick's successor Marilyn Tavenner, a former nurse and hospital chief executive who was secretary of the Virginia Department of Health and Human Resources.