Former U.S. Defense Secretary William Perry says that North Korea has the ability to produce one nuclear bomb a year.

Perry, whose remark appeared in Japan’s Nihon Keizai Shimbun on Wednesday, added that the U.S. should review its policies on North Korea before coordinating them with Tokyo and Seoul. He said that the U.S. should then consider sending a special envoy for direct talks with Pyongyang.

He added that the purpose of North Korea’s uranium enrichment program at Yongbyon appears to be to build light water reactors for generating power for peaceful purposes.

But he did not rule out the possibility that the reclusive country could have another facility for uranium enrichment to build nuclear weapons.

Perry claimed that the international community needs to send a strong message against North Korean nuclear development by imposing additional economic sanctions on the communist country.