China has claimed a greater portion of its continental shelf in the East China Sea in a document it recently submitted to the United Nations, in an apparent bid to raise its stake in territorial rows with its neighbors.

The U.N. Commission on the Limits of the Continental Shelf’s website showed on Sunday Beijing’s claim to the edge of its seabed beyond its 200 nautical mile (370 kilometer) exclusive economic zone from the baselines of its territorial waters.

The report, filed on Dec. 14, said “geomorphologic and geological features” prove that China’s ocean floor “naturally” stretches to the Okinawa Trough, some 200 kilometers from its coast. It also shows that in comparison with its preliminary filing, the country had slightly expanded its claim northeastward, widening the overlap with Korea’s claim. 

Seoul’s Foreign Ministry is expected to turn in its own formal statement as early as Wednesday. It reportedly plans to maintain the country’s outer limit of continental shelf is closer to Japan than it said in its 2009 claim, based on research by the state-run Korea Institute of Geoscience and Mineral Resources.

The contested areas are believed to hold vast crude and natural gas reserves.

“(The documents are) a partial submission concerning the outer limits of the continental shelf beyond 200 nautical miles in part of the East China Sea. This submission of the Chinese Government is without prejudice to any future submission by China on delineation of the outer limits of the continental shelf in the East China Sea and other seas,” a note verbale attached to China’s submission reads.

The U.N. CLCS is forecast to convene a session for a scientific review and recommendation in mid-2013.

The claims will likely trigger backlash from Japan, which rejected the initial documents presented by Korea and China in 2009 as a violation of its national interests. The two countries have been consulting with each other, apparently to counter Tokyo’s increasing maritime assertiveness.

Tension has been flaring between Japan and China over the islands of Senkaku or Diaoyu in the East China Sea. Tokyo also claims Korea’s islets of Dokdo in the East Sea.

Beijing is also seen as upping the ante in its future negotiations with Seoul by claiming a more northeastward boundary. The multinational agency’s advances have no binding power and in case of an objection by another country, it shelves discussions until the stakeholders settle themselves.

But the intense competition reflects the Asian powers’ efforts to gain recognition from the international community that may add weight to their respective claims, Seoul officials have said.

By Shin Hyon-hee  (heeshin@heraldcorp.com)