While pressing China to obey the "ruling" over the South China Sea issued by the Arbitral Tribunal in The Hague on Tuesday, Japan presses on with a questionable "island" claim.

"The next flash point could be a bit closer to home," Japan Times said on Wednesday, in reference to Okinotori, two rocky outcroppings measuring 9 square meters in all upon which it bases its claimed exclusive economic zone.

The United Nations Commission on the Limits of the Continental Shelf has dismissed that the Okinotori outcroppings constitute an "island".

At a news conference on Thursday, Japan's Chief Cabinet Secretary Yoshihide Suga argued that the tiny Okinotori, which lies about 1,700 km southwest of Tokyo, is an island.

Yet Tokyo urges China to accept the ruling of the Arbitral Tribunal in The Hague that China's 500,000-sq-m Taiping Island is a "rock", not an "island."

Japan has been spending large sums of money for more than two decades on buttressing Okinotori - now circled by concrete sea walls - from further erosion.

It maintains that as an "island", Okinotori can be used to map its exclusive economic zone in the East China Sea.

But in April 2012, in its recommendations on Japan's submission on the limits of its outer continental shelf, the United Nations Commission on the Limits of the Continental Shelf questioned Japan's claims based on Okinotori.

By defining the uninhabited rock as an "island", Japan illegitimately claimed an approximately 400,000 sq km exclusive economic zone, larger than the area of Japan itself.

According to the United Nations Convention on the Law of the Sea, which Japan signed in 1983, rocks that cannot sustain human habitation or economic life of their own may have no exclusive economic zone or continental shelf.

Okinotori has never been inhabited, and its economic life is disputable.

To substantiate the claim to the large EEZ around Okinotori, the Japanese government reportedly set aside 13 billion yen ($123 million) early this year for rebuilding storm-damaged facilities on the rock.

Zhao Jianwen, a researcher at the Institute of International Law of the Chinese Academy of Social Sciences, said that fact Okinotori is just a rock cannot be changed "in any sense" by any kind of excuse.

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