The United States said it was willing to give North Korea a few more days to meet its commitments after North Korea appeared to miss a deadline on Saturday to shut down a nuclear reactor.
Under a February 13 multilateral deal, Pyongyang agreed to shut down its Soviet-era Yongbyon plant within 60 days but it seems it has not made good on that pledge because of millions of dollars frozen in North Korean accounts at a Macau bank.
The United States has said the funds have been unblocked and should no longer be an issue.
"Our patience is not infinite ... but we feel that given that the kind of unexpected complexities that did arise in connection with some of the banking issues that it's probably prudent to give this thing a few more days," a senior U.S. official who asked not to be identified told reporters.
North Korea said on Friday it would soon check whether it could access about $25 million in the accounts at Macau's Banco Delta Asia, which were frozen after the United States said it suspected the bank of being involved in money laundering.
Pyongyang also said it remained committed to carry out the February 13 agreement "and will also move" when the money in the Macau bank was released.
"It is time now for the DPRK to make its move so that all of us can move forward," the U.S. State Department said in a written statement, referring to the country by its official name, the Democratic People's Republic of Korea.
The statement also said North Korea must immediately invite back International Atomic Energy Agency nuclear inspectors and begin shutting down Yongbyon to get energy aid promised under the Feb. 13 deal.
"It remains for the DPRK Korea) to realize fully its commitments ... by inviting back the IAEA immediately to begin shutting and sealing the Yongbyon nuclear facility," State Department spokesman Sean McCormack said in the statement.
McCormack said that would allow other nations to provide North Korea with the equivalent of 50,000 tons of heavy fuel oil as promised under the agreement among the two Koreas, China, Japan, Russia and the United States.
That deal called for it to shut down the Yongbyon plant by Saturday as a first step toward ending its nuclear program.
"The Chinese wanted us to show some patience for a couple of more days. There's a sense that the communication lines are open and the North Koreans understand the fact that these accounts are accessible to them," Assistant Secretary of State Chris Hill said before the U.S. statement was issued.
The top U.S. negotiator with North Korea also said he hoped for a resumption of six-party talks by the end of the month.
Hill said there had been a big diplomatic push to end the crisis. "We'd like to see a similar level of effort from the DPRK -- a level of effort that, frankly, we haven't been seeing," Hill said.
North Korea, which conducted its first nuclear test last October, has insisted the Macau bank money must be freed before it will comply with the February agreement.
"The Chinese made very clear to us that they support the arrangements in Macau," Hill said. "They support the decision of the Macau authorities to unblock the accounts."