Mr. Hill spoke as the director general of the United Nations atomic agency, Mohamed ElBaradei, said today that his 10-member team of inspectors had visited the nuclear complex in Yongbyon, 100 kilometers, or 62 miles, north of Pyongyang, and had verified that the reactor there was switched off, as North Korea had announced over the weekend.

“After tomorrow, we will be able to report, hopefully, that all of the five facilities have been shut down,” Mr. ElBaradei said, speaking in Bangkok.

He was referring to five facilities North Korea has agreed to shut down under a February agreement with the United States, South Korea, China, and Russia in return for an initial shipment of 50,000 tons of heavy fuel oil. The facilities include a radiochemical laboratory that extracts plutonium from spent fuel rods from the five-megawatt reactor in Yongbyon, and two new, bigger reactors under construction nearby.

Speaking to Fox News on Sunday, the United States’ national security adviser, Stephen J. Hadley, said that Washington’s aim was “ultimately dismantling that program, getting a full accounting of what they’ve been doing with any covert enrichment program and finally getting them to turn over any nuclear materials from which nuclear weapons have or could be made.”

A statement from the North Korean foreign ministry in Pyongyang on Sunday said that that will depend “on what practical measures the U.S. and Japan, in particular, will take to roll back their hostile policies toward” North Korea.

North Korea said the IAEA team was only allowed to “verify and monitor” the shutdown and was not allowed to inspect its nuclear sites.

That strips the agency of any ability to independently investigate how much plutonium and atomic bombs North Korea has produced from the Yongbyon facilities and what it has done with the uranium enrichment equipment that American officials say North Korea bought from Pakistan.