The United States said Friday that it expects the Democratic People's Republic of Korea (DPRK) to shut down its Yongbyon nuclear facility in weeks after the chief U.S. nuclear envoy paid a surprise visit to the country.

"We think it can be done in weeks. I'll leave it to experts in graphite-moderated nuclear reactors to tell you exactly how long you can do that, what the time period for safely shutting down and sealing that kind of reactor is. But I think, generally, for the laymen, it's a matter of weeks," State Department spokesman Sean McCormack said at a briefing.

The United States also expects the International Atomic Energy Agency (IAEA) to arrive in the DPRK for inspections in the coming days, McCormack said.

After his visit to the DPRK, Hill said Friday in South Korea that the DPRK showed readiness to promptly shut down its nuclear reactor.

The DPRK "indicated that they are prepared promptly to shut down the Yongbyon facility as called for in the February agreement," Hill said.

Under the agreement by the six-party talks reached on Feb. 13, the DPRK will shut down and seal its Yongbyon nuclear facility in return for aid and other guarantees, including a possible normalization of ties with the United States.