Former U.S. Assistant Secretary of State for East Asian and Pacific Affairs Kurt Campbell says that the U.S. has failed in all its efforts to hold dialogue with North Korea.

Japanese daily Yomiuri Shimbun quoted Campbell as saying that North Korean leader Kim Jong-un has never expressed his intention to hold dialogue with the U.S. since he took power. He added that North Korea has continued to reject the U.S.’ proposal for talks on denuclearization.

Campbell explained that North Korea’s plan to reactivate its nuclear reactor at its Yongbyon facilities would be regressive to talks on North Korea's nuclear program, noting it has become difficult to revive productive diplomacy at this point.

Campbell said Pyongyang’s recent tough rhetoric appears to be just propaganda and hasn't been accompanied by military moves.