LONDON, Nov 14 (Reuters) - Two Republican senators said on Wednesday they would block the confirmation of the head of a new U.S. regulatory office because they are unhappy about the way Treasury Secretary Timothy Geithner has handled the Libor rate-rigging scandal.

Republican Senators Charles Grassley and Mark Kirk said they would hold up a vote to confirm Richard Berner, a former Morgan Stanley economist who was appointed by President Barack Obama late last year to head the Office of Financial Research.