TOKYO - Secretary of State Condoleezza Rice said Wednesday the United States is ready to use the "full range" of its military might to defend Japan in light of North Korea's nuclear weapons test, and her Japanese counterpart drew a firm line against developing a Japanese bomb. The United States is concerned that Japan, South Korea or perhaps Taiwan may want to develop their own nuclear weapons programs to counter the threat from North Korea. Such moves would anger China, which already has nuclear weapons, and raise tensions in the region. Part of Rice's assignment on this week's hastily arranged trip to China, Russia, Japan and South Korea is to lessen the temptation to develop separate national nuclear programs by reaffirming the U.S. intention to defend the nations most at risk. In Japan, Rice said she reaffirmed President Bush's pledge, made the day of the North's test last week, "that the United States has the will and the capability to meet the full range — and I underscore the full range — of its deterrent and security commitments to Japan," Rice said following discussions with Japanese Foreign Minister Taro Aso. Rice's words were a reminder to U.S. allies that the United States does not want to see a new nuclear arms race in Asia, but will likely be taken also as a warning to North Korea that it could face the U.S. nuclear arsenal if it used a nuclear weapon on a neighbor. The United States has repeatedly said t does not intend to attack North Korea or topple its communist regime. Shortly before Rice arrived, Aso said Japan should openly discuss whether it wants to possess nuclear weapons. He told a parliamentary committee the government has no plans to stray from its post-World War II policy of not allowing nuclear bombs on Japanese soil, "But I think it is important to discuss the issue." Even discussing the issue is extremely sensitive in Japan, with its troubled military history and experience as the only nation where nuclear weapons were used in wartime. With Rice at his side, Aso did not repeat the need for a discussion. "The government is absolutely not considering a need to be armed by nuclear weapons," Aso said. "We do not need to acquire nuclear arms with an assurance by Secretary of State Rice that the bilateral alliance would work without fault." Later Wednesday, Japanese Prime Minister Shinzo Abe insisted his government would not even discuss building a nuclear bomb. "That debate is finished," Abe testily told reporters. It was at least the third time since North Korea's test that Abe — a hawk on defense issues who came to office last month promising a more assertive Japan — has had to reassure jittery neighbors and an anxious United States that Tokyo would not abandon its postwar ban on nuclear weapons. Speaking to reporters Tuesday en route to Japan, Rice said North Korea's recent underground nuclear test "does carry with it the potential for instability in the relationships that now exist in the region." "That's why it's extremely important to go out and to affirm, and affirm strongly, U.S. defense commitments to Japan and to South Korea," Rice said. In addition to settling nerves among allies, Rice's Asia trip is meant to reinforce pressure on South Korea and especially China to enforce economic sanctions. Those include what the United States describes as an aggressive inspection and interdiction program that stops short of a full blockade of North Korean trade. China's U.N. Ambassador Wang Guangya said Tuesday that China would implement the resolution to the degree of inspections, but not interdiction. "Inspection is different than interdiction and interception," Wang told reporters on Monday. "I think different countries will do it different ways." Rice would not comment in detail about worries by the U.S. and other governments that the North may be preparing for a second test explosion. "We're concerned about further action by the North Koreans," Rice said, "but further action by the North Koreans will only deepen its isolation, which is pretty deep right now." Concern over a second test stems partly from new satellite imagery showing increased activity around at least two other North Korean sites, a senior defense official said Tuesday.