A top North Korean official said the US must lift sanctions against his country before it will shut down its nuclear reactor as part of an international disarmament deal, news reports said Friday. North Korean Vice Foreign Minister Kim Kye Gwan, making a brief, surprise stopover at Tokyo's main international airport late Thursday en route to Beijing from New York, said Pyongyang would be watching Washington's moves closely, the mass-circulation Yomiuri newspaper said. "The United States promised to resolve the problem of sanctions against our country within 30 days. If this promise is kept, then we will shut down our nuclear facilities in 60 days," said Kim, the chief negotiator to the disarmament talks, the Yomiuri reported. The Asahi newspaper and Kyodo News agency carried similar reports.