U.S. Secretary of State Condoleezza Rice arrived in Tokyo on Wednesday for talks with Japanese officials amid fears North Korea could be readying for a second nuclear test.

Rice was to meet with Japanese Foreign Minister Taro Aso, Defense Agency chief Fumio Kyuma and Chief Cabinet Secretary Yasuhisa Shiozaki to discuss sanctions against Pyongyang.

Rice was also to meet with Prime Minister Shinzo Abe on Thursday before she and Aso fly to Seoul for three-way talks with their South Korean counterpart, Ban Ki-moon.

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Of immediate concern was the prospect of North Korea following its Oct. 9 test with a second nuclear detonation, a move that would heighten tensions further.

South Korea urged the North on Wednesday not to take any action that would conflict with a U.N. resolution sanctioning Pyongyang for the test.

Rice will arrive as Japan is debating how far it can go to join in helping the U.S. military to board and search North Korean ships as allowed under U.N. Security Council sanctions passed over the weekend.

Japan's pacifist constitution bans the armed forces from offensive actions, and it was unclear whether such searches on the high seas would violate the charter.

The national Yomiuri newspaper reported Wednesday that Japan was expected to offer naval backup for those searches when Rice arrived in Tokyo.

Japan plans to dispatch destroyers, P-3C patrol aircraft and surveillance planes to waters near Japan to search for or pursue suspicious vessels and assist the inspections, the paper said.

Rice was also expected to reassure Tokyo that the U.S., which bases some 50,000 troop in Japan, is committed to the country's defense.

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The secretary told reporters accompanying her to Japan that Washington was concerned the North Korean test could spark an arms race in the region, and that it was important to tell U.S. allies Japan and South Korea that Washington's defense umbrella was dependable.

Abe has pledged that Japan — the only country ever attacked with atomic weapons — would stick to its ban on possessing or producing nuclear weapons, but some officials have said that Tokyo should discuss its defense options.