Human rights issues should become the central principle of U.S. policy toward North Korea, a director of the nongovernmental organization U.S. Committee for Human Rights in North Korea said Monday in Tokyo.

Rabbi Abraham Cooper, also an associate dean of the Jewish human rights group Simon Wiesenthal Center, told reporters that diplomacy focused on denuclearization has failed to produce results during the two previous U.S. administrations.

"We really haven't made great progress despite all the efforts made," he said at the Foreign Correspondents' Club of Japan, and U.S. President Barack Obama should shift tactics.

Cooper pointed out that leverage of human rights issues by the U.S. bore significant fruit in ending the Cold War, with small steps ultimately setting the stage for deconstruction of the Soviet bloc and an end to nuclear fears.

Cooper, who is also vice chairman of the North Korea Freedom Coalition, which represents more than 70 international NGOs, said the group sent a letter Monday to U.S. Secretary of State Hillary Clinton asking her to meet with relatives of the Japanese people who were abducted by Pyongyang and are still missing.

During his stay in Japan to meet with the relatives and their supporters, he also spoke with Diet members and Foreign Ministry officials and proposed holding an international meeting in Tokyo to discuss Pyongyang's human rights violations.

Tokyo should hold a two-day international tribunal "not in a legal sense, but in a symbolic sense" to address the North's human rights abuses, he said.