North Korea said Tuesday it has stopped disabling its nuclear reactor and will consider restoring the plutonium-producing facility in anger over Washington's failure to remove it from the US list of terror sponsors. The North's statement marks the emergence of the biggest hurdle yet to the communist nation's denuclearization process and is expected to escalate tension in the nuclear talks involving China, Japan, the two Koreas, the U.S. and Russia. Pyongyang's Foreign Ministry said it suspended the disablement work at the reactor and other facilities at its Yongbyon nuclear complex as of Aug. 14 because the US did not keep its promise to delist Pyongyang as a terror sponsor under last year's deal. The suspension was notified to countries concerned, the ministry said in a statement carried by the official Korean Central News Agency. The ministry said it was forced to take the step "as countermeasures in a situation where the United States violated the agreement." It also said the country will "consider restoring the Yongbyon facilities to their original states" but did not say when it would do so. Removal from the terror list is one of key concessions offered to the North in exchange for shutting down and disabling the reactor under a landmark six-nation deal reached last year. The US announced in June that it would delist the North as a terror sponsor after Pyongyang turned in a long-delayed list of its nuclear programs. The two sides have been negotiating how to verify the nuclear declaration, with Washington saying it would remove the North from the terror list only after Pyongyang agrees to a verification plan. The North's statement came shortly after Chinese President Hu Jintao left South Korea after summit talks with President Lee Myung-bak that included discussions on the North's nuclear issue. South Korea's Foreign Ministry was not immediately available for comment. The presidential Blue House referred the queries to the Foreign Ministry.