The Bush administration has announced plans to go ahead with building the nation’s first new nuclear weapon in nearly two decades. On Friday, the National Nuclear Security Administration selected the Lawrence Livermore National Laboratory to design a new nuclear warhead to replace older ones. The United States still maintains an arsenal of 6,000 nuclear warheads. Sen. Dianne Feinstein of California criticized the move to create a new nuclear warhead at a time that the United States is pushing other countries to drop nuclear weapons programs.