A top North Korean official said the U.S. 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 reported.

"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 Asahi newspaper and Kyodo News agency carried similar reports.

Under a Feb. 13 agreement reached at six-nation talks in Beijing, North Korea must shut down its main nuclear reactor and allow U.N. inspectors back into the country within 60 days. In return, the North would receive aid equal to 50,000 tons of heavy fuel oil from the other countries in the talks — the United States, South Korea, Russia, China and Japan.

North Korea pointed to what it called unfair U.S. sanctions as a reason to boycott disarmament talks for more than a year. The restrictions were still a sore point when the North returned to talks in December. The North Korean negotiator refused to discuss the country's weapons until Washington budged.

An agreement to resolve the matter within 30 days was key to a potential breakthrough deal that the North struck Feb. 13.

Kim had been in New York for the first meeting of the U.S.-North Korea Working Group, one of five established under the February agreement.