Beijing ? North Korea missed a Saturday deadline for shutting down its main nuclear reactor, and a key U.S. negotiator said the country must keep the disarmament program from foundering.

The United States and other governments involved in six-nation talks on North Korea’s nuclear programs said the slipping of the 60-day deadline was significant, but not yet fatal to a two-month-old agreement that laid out a timetable for disarmament.

“It’s time for the North Koreans to get moving on their issues,” Assistant Secretary of State Christopher Hill, the chief U.S. negotiator, told reporters after meeting in Beijing with his Chinese counterpart.

Hill ticked off the unmet conditions of the February agreement: North Korea’s failure to shutter its Yongbyon reactor and allow verification by U.N. inspectors, and South Korea’s resulting refusal to ship 50,000 tons of fuel oil to 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.