Foreign Minister Yoriko Kawaguchi told delegates attending a conference on the Comprehensive Nuclear Test Ban Treaty that enacting it would help the world achieve peace.
But the conference, which drew hundreds of delegates to Vienna, was overshadowed by concern over North Korea's and Iran's nuclear programs. The Bush administration also underlined its opposition to the treaty by not formally attending the opening session.
Kawaguchi also met with Mohamed ElBaradei, head of the International Atomic Energy Agency, for talks that touched on North Korea's nuclear program and Japan's interest in quickly enacting the treaty.
"Since Japan is the only country in the world to have suffered the tragedy of atomic bombing, we Japanese people have a particularly strong desire for a ban on nuclear testing," she said. "At this conference, it will be important for us to send a strong message once again, urging states that have not signed or ratified (the treaty) to do so at the earliest possible date."
The United States led the negotiations to convert a moratorium on testing into a permanent treaty in 1996, but the U.S. Senate rejected the treaty two years later, thwarting arms control advocates and the administration of former President Clinton.
Bush, like Clinton, has imposed a voluntary moratorium. But some administration officials have suggested that tests may be necessary if there is a decision to develop new U.S. nuclear weapons.
The U.S. position jeopardizes the treaty itself. As one of 44 countries with nuclear power or research facilities listed in an annex to the treaty, the Americans must ratify the document or it won't go into effect.
North Korea also has raised concern by saying it plans to test a nuclear device as part of its weapons program, while the United States accuses Tehran of wanting to develop nuclear arms.
So far, 32 countries listed in the annex have accepted the treaty. The document is considered a critical element in efforts to stop the spread of nuclear weapons, since a ban on testing would make developing such arms almost impossible.
U.N. Secretary-General Kofi Annan put his weight behind the conference and its aims.
"Our world can ill afford to fail, or even to be unduly delayed, in achieving a comprehensive nuclear test ban," he said. "Delay increases the risk that nuclear testing might resume, and it jeopardizes efforts to take further steps towards the goal of nuclear disarmament."
By Danica Kirka