The top U.S. envoy to North Korea nuclear disarmament talks said Saturday he expects Pyongyang to shut down its plutonium-producing reactor in a matter of days.

"I think it's a matter of today, tomorrow, maybe Monday," U.S. diplomat Christopher Hill told reporters in the resort town of Hakone south of Tokyo

Hill said he could not confirm the exact date but added, "I hope soon we'll be hearing about the shutdown of the Yongbyon facility, and that will be a good day for the six-party process."

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Hill also said he expected the North to submit a list of its nuclear facilities within months, as was agreed to in February's round of talks.

Hill, who came to Japan to prepare for another round of the six-nation nuclear talks next week in Beijing, stressed that shutting down the North's Yongbyon reactor would be the first step toward complete denuclearization.

"The big issue is not the shutdown, it's how the shutdown will lead to the next step and eventual disablement," he said.

The North's list of its nuclear facilities was expected to be "the next big issue" at the talks, Hill said. He said he also hoped to get "some concept of the time schedule" going forward at the next six-party talks.

The other parties in the talks — which include the Koreas, China, Japan, Russia and the United States — need to keep their end of the bargain to send energy aid to North Korea to ensure Pyongyang will keep its end of the bargain, he said.

North Korea agreed earlier this year to shut down its reactor and take other steps toward disarmament in exchange for oil and other financial and political concessions in a deal with the United States, China, Japan, South Korea and Russia.

Hill said his departure for Seoul, originally scheduled to take place Sunday, may be postponed until Monday because of a powerful typhoon approaching the Tokyo area. The delay would push back his departure from Seoul for Beijing to Tuesday, he said.

Complete coverage is available in FOXNews.com's North Korea Center.