In 1967, then Prime Minister Eisaku Sato declared Japan's three-point nonnuclear principle of not "producing," not "possessing" and not allowing the "bringing in" of nuclear weapons. The third point has been interpreted to mean that Japan will not allow either the stationing or transiting of nuclear weapons on its territory.

But in recent media interviews, Mr. Ryohei Murata, who served as vice minister of the Foreign Ministry from 1987 to 1989, admitted the existence of a secret pact between Japan and the United States under which Tokyo would tacitly approve the stopover of U.S. military ships or aircraft carrying nuclear weapons in Japan and their transit through Japanese territorial waters. The pact was agreed on when Japan and the U.S. revised the bilateral security treaty in 1960. He also said that he would speak in the Diet if summoned.

The security treaty says that the U.S. will hold "prior consultations" with Japan when it makes major changes in the deployment and equipment of the U.S. forces in Japan and when it uses Japanese bases for military operations outside Japan that are not related to the defense of Japan.

The government has been saying that no secret pact dealing with U.S. ships and aircraft carrying nuclear weapons exists, and that nuclear weapons were not "brought into" Japan because prior consultations were never held. But Mr. Murata's statement appears to have completely undermined the government's effort to hide the truth about the existence of such a pact. Mr. Murata said that he took over a document stating the pact from his predecessor and handed it over to his successor. He also said that he notified Foreign Ministers Tadashi Kuranari and Sosuke Uno about the pact.

U.S. diplomatic documents declassified in the late 1990s substantiated the existence of the pact. Also in the 1990s, the U.S. removed tactical nuclear weapons from surface ships, submarines and land-based naval aircraft.

Given these facts, it is hard to understand why the government continues to hide the truth. Instead, it should seek to regain people's trust by disclosing the truth and explaining why the secret pact was necessary.