"It's unfortunate that at a time when our nation is facing enormous challenges, many in Congress have decided to delay critical nominations for political purposes," Obama said in a written statement announcing the appointment.
White House Communications Director Dan Pfeiffer said the appointment was necessary to carry out the healthcare law, which calls for sweeping changes in the two programs that insure about a third of all Americans.
Obama decided to make the appointment while Congress was in recess because "many Republicans in Congress have made it clear in recent weeks that they were going to stall the nomination as long as they could, solely to score political points," Pfeiffer told The New York Times.
As a recess appointee, Berwick has all the powers of a permanent appointee, but his appointment will expire at the end of the next congressional session in late 2011.
Obama nominated Berwick to be administrator of the Centers for Medicare and Medicaid Services in April. The agency hasn't had a permanent administrator since October 2006.
At the time of his nomination, Senate Republicans said they would challenge Berwick, reported by several media outlets to be a supporter of the government-run healthcare system practiced in Britain, Politico reported. During the bruising and heated healthcare debate, Obama insisted he did not want the U.S. system to duplicate the British system.
Sen. Pat Roberts, R-Kan., said the recess appointment "proves the Obama administration did not have the support of a majority of Democrats and Republicans in the Senate and sought to evade a hearing."