Japanese Foreign Minister Taro Aso, after a meeting with Secretary of State Condoleezza Rice, said today his country has "no position at all to consider going nuclear" and would continue to rely on a half-century-old defense treaty that covers Japan with a U.S. nuclear umbrella.

Rice, on the first stop of an Asian tour meant to respond to the North Korean test, underlined U.S. defense commitments to its Asian allies in hopes of heading off a nuclear arms race that could spread to Japan, South Korea and Taiwan.

She was to fly Thursday to South Korea.

The United States has "the will and capability to meet the full range of its deterrent and security commitments," she said. "A U.S. commitment to defend Japan ... will be maintained under any circumstances."

Japan, which has an advanced civilian nuclear program, could build a nuclear weapon quickly if it chose to do so. But public sentiment in the only nation to have been struck by nuclear bombs — by the United States during World War II — remains strongly opposed to developing an atomic arsenal.

The major fear in the region appears to be not that North Korea would attack a neighbor with a weapon but that it might transfer nuclear technology to another rogue state or terrorist group.

Beyond reaffirming U.S. defense commitments to Japan and South Korea, Rice is discussing how to help countries in the region detect and stop such nuclear trafficking.

In Tokyo, she said the Bush administration would offer radiation detection equipment and other technology to those who need it. Japan has blocked all North Korean ships from entering the country but it is not clear if Japan or other Asian nations would attempt to board a North Korean vessel in international waters.

Meanwhile, the North Korean regime may be tempted to test again, while Rice is in the region, to show its defiance of her and of new sanctions imposed by the U.N. Security Council, said Kenneth Quinones, a former State Department intelligence expert on North Korea who directs the global studies program at Akita International University north of Tokyo.

"The more pressure you put on (North Korean leader) Kim Jong Il, the more determined he is to show he'll stand up to U.S. imperalism," Quinones said.

Asked about reports of new activity at the same remote site where North Korea staged an underground nuclear test last week, Rice urged the North Korean government to "exercise maximum self-restraint."

North Korea on Tuesday staged a massive torch light parade in Pyongyang to show its defiance of foreign demands that it give up the program and abide by the Security Council resolution, which calls for it to return to six-nation talks.

Quinones said that it was possible that North Korea would return to negotiations, which have been stalled for a year, if the Bush administration accepted a North Korean proposal to transfer $24 million in frozen North Korean assets from a Macao bank to a New York financial institution. The bank froze the money at U.S. behest a year ago on suspicion that the funds came from counterfeiting and other illegal activities. North Korea has made lifting the freeze a precondition for new nuclear negotiations.