Japan should consider building a military base on islands disputed with China to counter Beijing's rising assertiveness, a leader of Japan's opposition said Monday on a visit to the United States.

Nobuteru Ishihara, sometimes seen as a future prime minister if his Liberal Democratic Party returns to power, said that Japan should also look more broadly at stepping up defense spending in the face of a rising China.

Asia's two largest economic powers dispute control of a set of uninhabited islands -- known as the Senkaku in Japanese and the Diaoyu in Chinese -- where Japan's arrest last year of a Chinese fishing captain led to a standoff.

Ishihara, secretary general of the conservative opposition party, said that Japan should move "quickly" to put the islands under public control. Tokyo considers most of the area to be privately owned by Japanese citizens.

"Following this change, a port should be developed where fishing boats may take refuge," Ishihara said at the Hudson Institute, a Washington think-tank.

"I further believe that we must seriously begin contemplating the establishment of a permanent post for the Self-Defense Force in this area," he said, referring to officially pacifist Japan's armed forces.

Japan said in 2008 that it reached an agreement with China for joint development of potentially lucrative gas fields near the disputed islands. But the deal has gone nowhere, with China saying its stance has not changed.

Prime Minister Yoshihiko Noda's Democratic Party of Japan -- which swept out the long-ruling Liberal Democrats in a 2009 election -- has mostly sought smooth ties with China, which says its growing military spending is for peaceful purposes.

But Ishihara said that China has become "assertive, one may even say aggressive," in recent years and pointed to its actions in separate maritime disputes with the Philippines, Vietnam and other Southeast Asian nations.

"Emboldened by its new economic weight and growing military might, China's proclamations of its 'peaceful rise' appear more and more at odds with the emerging reality," Ishihara said.

Ishihara is the son of Tokyo Governor Shintaro Ishihara, an outspoken nationalist.