U.S. President Barack Obama, left, and his Russian counterpart Dmitry Medvedev, right, sign the 'New START'  nuclear arms reduction treaty at Prague Castle Thursday, April 8, 2010. (AP Photo/CTK, Roman Vondrous)

Photo by: ROMAN VONDROUS

U.S. President Barack Obama, left, and his Russian counterpart Dmitry Medvedev, right, sign the 'New START' nuclear arms reduction treaty at Prague Castle Thursday, April 8, 2010. (AP Photo/CTK, Roman Vondrous)