The Bush administration said Saturday that North Korea must follow through on its promise to shut down and seal its nuclear reactor, but held back from criticizing Pyongyang for missing a Saturday deadline to do so. Pyongyang had committed to take the step by Saturday as part of an agreement reached in February between it and five other nations _ the United States, China, Japan, South Korea and Russia _ to end its nuclear weapons program. But Washington also failed to resolve within 30 days of the agreement, as promised, a dispute with North Korea over funds frozen through U.S. sanctions. Full Story