A leader of Japan's main opposition party wants deeper relations with the United States and would consider increasing defense spending because of China's rising military power and forceful territorial claims in disputed seas.

Nobuteru Ishihara, secretary-general of the conservative Liberal Democratic Party, said Monday that Japan's security alliance with the United States is a source of regional stability amid uncertainty over what he described as aggressive Chinese behavior.

He contended that China's military priority of being able to attack Taiwan, a self-governing island Beijing regards as part of China, had been enlarged to achieve complete maritime dominance in the East and South China Seas.

"As a major Asian trading nation, and as a longtime ally of the United States, Japan has a direct stake in this issue, and by working with your country, we can make important contributions to ensure that this region remains open and safe," Ishihara told the Hudson Institute think tank in Washington.

He suggested that Japan could "share the burden" with the U.S. should the need arise to dispatch navy ships to the Taiwan Strait.

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He also said his party, should it take power, is discussing increasing Japan's defense spending, currently equivalent to about 1 percent of gross domestic product. It was considering advocating revisions to Japan's pacifist constitution for troop deployments overseas, currently restricted to U.N. peacekeeping operations, that would strengthen the U.S.-Japan security alliance, he said.

Ishihara is seen as a possible candidate for prime minister should the Liberal Democratic Party win power again. The party ruled nearly continuously for five decades until it lost 2009 elections to the Democratic Party of Japan, which has since fielded three prime ministers.

The DPJ initially moved to loosen Japan's tight ties with Washington, then backed away from a campaign promise to move a U.S. military base out of the southern island of Okinawa. Yoshihiko Noda, who became prime minister in September, is seen as pro-U.S.

Ishihara claimed the alliance with the U.S. could yet fracture under the DPJ, although he also said Japan's relationship with Washington enjoys bipartisan support. That was underscored by huge American support when Japan suffered massive earthquake and tsunami in March that left nearly 20,000 people dead or missing.