According to reports from Reuters, a United States official has said North Korea is demanding the first shipments of its promised 50-thousand tons of heavy fuel before it begins initial steps toward denuclearization.

The U.S. official, who spoke on the condition of anonymity, said North Korea seems to want to start receiving the agreed fuel as they move forward in shutting down its nuclear facilities in Yongbyon.

Reuters reported that the official added Pyongyang had notified South Korea and the International Atomic Energy Agency of these desires.

Some are raising concerns that the North’s requests may slow down implementation of a nuclear agreement drafted by six nations, but top U.S. officials doubt that the shutdown of the Yongbyon reactors will be delayed.