WASHINGTON, April 14 (Reuters) - The U.S. Congress on Tuesday approved a bill to repair the formula for reimbursing Medicare physicians, marking a rare bipartisan achievement just in time to head off a 21 percent cut in the doctors' pay.

Final action came as the Senate voted 92-8 to approve the so-called doc fix; the House of Representatives had acted over two weeks ago. The bill now goes to President Barack Obama for his expected signing into law.

(Reporting by Susan Cornwell; Editing by Eric Beech)