The chief US negotiator at North Korean nuclear disarmament talks was expected to arrive in China on Tuesday for talks on implementing an accord meant to disable the North's nuclear reactor, the State Department said Monday. Christopher Hill, an assistant secretary of state, may have meetings in Beijing with his North Korean counterpart but the matter had yet to be settled, State Department spokesman Sean McCormack told reporters. Under a February agreement, North Korea promised to abandon its nuclear ambitions in return for 1 million tons of oil as well as political concessions. The North has already shut down its sole operating nuclear plant at Yongbyon in return for a shipment of 50,000 tons of oil. It recently pledged to disable Yongbyon and declare all its nuclear programs by year's end.