North Korea failed to meet a year-end deadline to declare all its nuclear programs under an aid-for-disarmament deal, prompting disappointed reactions Monday from South Korea, the United States and Japan. The three countries, along with China and Russia, have been pushing North Korea to abandon its nuclear programs in a series of negotiations that began in 2003 and finally gained momentum in 2007.Washington and Seoul have said they believe that the overall disarmament process, though falling behind schedule, is still on track.