BEIJING (AP) – North Korea failed to meet a Saturday deadline for shutting down its main nuclear reactor, and the top American nuclear negotiator said the delay was draining momentum from a disarmament plan for the North.

Saturday’s missed deadline marked the latest setback for an agreement that when reached in February offered the prospect of disarming the world’s newest declared nuclear power. North Korea successfully exploded a nuclear bomb in October.

“We don’t have a lot of momentum right now. That is for sure,” American Assistant Secretary of State Hill told reporters before meeting his Chinese counterpart, Wu Dawei.

The disarmament plan, reached after nearly four years of arduous negotiations, laid out a timetable for North Korea to dismantle its nuclear programs. The plan was unexpectedly disrupted by a dispute over frozen North Korean funds in a Macau bank that Washington said this past week was finally resolved.

On Friday, Mr. Hill did not say what the consequences would be if the North missed the Saturday deadline.

“There is no reason why the DPRK can’t get on with the task of denuclearization,” said Mr. Hill, using the official name of the Democratic People’s Republic of Korea.

“We are not indifferent to missing a deadline. Obviously it is a very important date,” he said. “We will work with our other partners on the appropriate response to the current circumstances.”

As part of the disarmament agreement, the North was supposed to gain access to $25 million in frozen funds at the Banco Delta Asia bank in the Chinese territory of Macau. The bank was blacklisted by Washington in September 2005 for allegedly helping the North launder money and pass counterfeit $100 bills.

The funds were unblocked this week, but North Korea’s Foreign Ministry said Friday it was still confirming the release. The Ministry said the country would carry out its side of the February agreement “when the lifting of the sanction is proved to be a reality.”

North Korea alarmed the world when it conducted its first-ever underground nuclear test. After a 13-month boycott of nuclear talks, it agreed in February with America, China, South Korea, Japan and Russia to give up its nuclear programs in exchange for energy aid and political concessions, along with an American promise to resolve the bank issue.

Macau’s Monetary Authority, which has taken control of the bank, has been tightlipped about the process of releasing the frozen funds.

But Mr. Hill said Friday that America considered the problem resolved.

“It’s certainly worrisome to all of us to see them approaching this date rather lethargically. … We understood their concerns about the banking issue and frankly those concerns have been met,” he said.

American officials and experts say the process of shutting down a reactor and having U.N. nuclear inspectors verify it would take at least several days – making it virtually impossible for the North to meet the Saturday deadline.

“It’s a technical question, but it does not take that long,” Mr. Hill said. “We’re not talking months or anything like that. There should be no reason to go slow in this process.”

He would not say how long the other countries would wait for North Korea to act on its promises.

“I don’t want to put a date or an hour, but another month is not in my constitution,” he said.

The only immediate cost the impoverished North would suffer for not shutting the reactor by the deadline would be an initial 50,000 ton shipment of heavy fuel oil promised as a reward. That shipment was part of 1 million tons of oil it would get for dismantling its nuclear program.

However, it is unlikely America. or other countries would take any punitive action, as Washington also failed to resolve the bank issue within 30 days as promised.

The International Atomic Energy Agency, the U.N.’s nuclear watchdog, was still awaiting an invitation from North Korea for a preliminary visit, a diplomat familiar with the issue said on condition of anonymity because he was not authorized to speak to reporters.

After a visit by two senior IAEA officials to establish procedures for an inspection tour, the agency’s board would meet to approve the first return of inspectors since December 2002, when North Korea kicked them out and quit the Nuclear Nonproliferation Treaty. The process could take weeks.