TOKYO – The United States is willing to use its full military might to defend Japan in light of North Korea’s nuclear test, Secretary of State Condoleezza Rice said Wednesday as she sought to assure Asian countries there is no need to jump into a nuclear arms race.

At her side, Rice’s Japanese counterpart drew a firm line against his nation developing a nuclear bomb.

The top U.S. diplomat said she reaffirmed President Bush’s pledge, made hours after North Korea’s Oct. 9 underground test blast, “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 spoke following discussions with Japanese Foreign Minister Taro Aso, the first stop on her crisis mission to respond to the threat posed by the North.

Back home, President Bush told ABC News that if the U.S. learned North Korea was about to transfer nuclear technology to others, the communist nation would face “a grave consequence.” He did not elaborate.

“I want the leader to understand – the leader of North Korea to understand that he’ll be held to account,” Bush said, referring to the country’s ruler, Kim Jong Il.

Signs continued Wednesday that North Korea might be readying for a second nuclear test that could be carried out as soon as this week, while Rice is in Asia.

There were reports that North Korea had told China it was ready to conduct up to three more nuclear tests. But at the State Department in Washington, spokesman Tom Casey said, “We certainly haven’t received any information from them, from the Chinese, that they’ve been told by Pyongyang that another test is imminent.”

U.S. government officials, who spoke on condition of anonymity because of the sensitive situation, said there wasn’t evidence to suggest that another nuclear test in North Korea was hours or even days away.

But given the underground nature of the testing, officials said, it could happen with little or no warning. Analysts have been monitoring the movement of trucks and VIP buses around test sites as well as military communications, media and official travel.

In Seoul, South Korea, the country’s foreign minister – who has been selected to become the next secretary-general of the United Nations – warned the North not to detonate again.

“If North Korea conducts an additional test, the response of the international community will be much more serious,” he said, providing no further detail.

Christopher Hill, the State Department’s lead negotiator on North Korea, said on National Public Radio’s “Morning Edition” that there are “some indications” of a possible second test by the North, but he added, “We do not have any indication that it’s going to happen imminently.”

Rice’s reference to U.S. willingness to honor the “full range” of the nation’s might was meant as a signal to allies that the United States does not want to see them embarking on a new nuclear arms race to protect themselves. It was also likely to be taken as a reminder to North Korea that, should it use nuclear weapons on a neighbor, the U.S. has powerful forces of its own.

Associated Press writer Katherine Shrader in Washington contributed to this report.