The Bush administration said Saturday that North Korea must follow through on its promise to shut down and seal its nuclear reactor, but held back from criticizing Pyongyang for missing a Saturday deadline to do so.

Pyongyang had committed to take the step by Saturday as part of an agreement reached in February between it and five other nations — the United States, China, Japan, South Korea and Russia — to end its nuclear weapons program. But Washington also failed to resolve within 30 days of the agreement, as promised, a dispute with North Korea over funds frozen through U.S. sanctions.

Technical difficulties meant the $25 million in North Korean assets held at a bank in the semiautonomous Chinese territory of Macau were just freed this past week.

So North Korea now says it will allow U.N. inspectors back and shut down its Yongbyon reactor only after it confirms that the funds were released. It wanted 30 days to do so, but a visiting U.S. delegation rejected that. The Yongbyon reactor is believed to have produced plutonium for the October underground test blast that ushered North Korea into the community of nuclear nations.

"It is time now for the DPRK to make its move so that all of us can move forward," State Department spokesman Sean McCormack said, using the official name of the Democratic People's Republic of Korea.

Washington's chief negotiator with North Korea also refrained from directly criticizing the North.

"We don't have a lot of momentum right now. That is for sure," Assistant Secretary of State Christopher Hill said in Beijing. "There is no reason why the DPRK can't get on with the task of denuclearization."

A senior State Department official said Washington believes the process of shutting down and sealing Yongbyon must happen as fast as possible.

But the official, who spoke on condition of anonymity to more freely discuss the U.S. view, said the North's failure does not endanger the agreement. The sides are probably only a few days behind where they needed to be under the agreement, and it is not just Pyongyang that is at fault in any case, the official said.

Washington is listening to Chinese calls for patience in the matter, the official said, leaving open the possibility that North Korea could receive 50,000 tons of heavy fuel oil it was promised in return for shutting down the reactor merely if it verifiably begins the process.

The Saturday deadline was one of the less difficult in a long and uncertain process outlined by the agreement.

Under the deal, Washington also promised to talk with Pyongyang about normalizing relations with the communist regime and establishing a permanent peace settlement to replace the cease-fire that ended the Korean War in 1953.

Later steps by North Korea include dismantling all its atomic facilities, though no timeline has been set.

Also left for later discussion would be what to do with the atomic weapons the North now is believed to possess — a half-dozen or more by expert estimates. North Korea also would have to declare all its nuclear programs that would be disabled. Washington has accused Pyongyang of having a separate uranium enrichment program, but North Korea has never acknowledged it.