Japan pledged aid worth up to half a billion dollars to Pacific island nations Saturday at a summit stressing the importance of maritime law in a region warily eyeing China's growing might at sea.

At the close of a two-day meeting on the southern Japanese island of Okinawa, leaders from 16 nations and one territory produced a joint declaration emphasising the need for international rules to be obeyed on the oceans.

"The leaders acknowledged the importance of promoting maritime cooperation, in such areas as marine environment, maritime security, maritime safety... to promote economic growth and to improve livelihoods and food security," the declaration said.

The pronouncement from the summit, which groups Pacific island nations alongside Australia, New Zealand and Japan, comes as China grows ever more assertive of its claims on areas of sea far from its mainland coast.

Beijing is currently involved in an increasingly bitter stand-off with Manila over a shoal off the Philippines' western seaboard, which has impacted trade ties and iced relations.

Japan has also clashed with China over disputed outcrops, notably the strategically coveted Senkaku islands, which Beijing calls Diaoyu, known to harbour rich fishing grounds and believed to sit atop valuable mineral beds.

In a forum Japan views as an important plank of its soft-power strategy, Prime Minister Yoshihiko Noda said Tokyo would be funding an insurance programme aimed at helping Pacific island countries deal with natural disasters.

In concert with the World Bank, the scheme is intended to provide short-term liquidity to governments in the event of a catastrophe like the earthquake-tsunami that hit northeast Japan in March 2011.

In addition to the insurance scheme, which has a reported price tag of $5.7 million, Tokyo will also look to give up to half a billion dollars in aid to Pacific Island countries.

"Our fiscal situation is tight due to the disaster," Noda told a press conference. "However, we will not be inward-looking but seek to be a country that will continue to contribute to the peace and prosperity of the world."

The $500 million, to be served up over the coming 36 months, mirrors the figure Tokyo gave the region over the previous three years. Details of what the money would fund were not immediately available.

The summit, the sixth of its kind since 1997, is one prong of Tokyo's charm offensive to garner support in its bid for a permanent seat on the UN Security Council.

Fiji, a member of the Pacific Islands Forum, skipped this year's summit, the Kyodo News agency reported. Japan last week said it had not invited Fijian strongman Voreqe Bainimarama amid concerns his moves towards restoring democracy have not gone far enough.

Had Bainimarama attended the Pacific Islands Leaders Meeting (PALM) in Japan, it would have signalled the isolated regime leader's first major opportunity to return to the international community after years of ostracism.