In his summits with Presidents Hu Jintao of China and Roh Moo Hyun of South Korea last week, Prime Minister Shinzo Abe took the first step toward improving relations that had soured between Japan and the two countries under the rule of his predecessor, Junichiro Koizumi. His initiative also opened a new horizon in Japan's diplomacy in Asia.

North Korea's nuclear test, carried out during Abe's summit diplomacy, signals a direct security threat to Japan and the rest of Asia, as well as a threat to the nuclear nonproliferation system.

The adoption of a resolution by the U.N. Security Council calling for sanctions against North Korea should be regarded as the first fruit of cooperation between Japan and China, and Japan and South Korea, at a summit.