Metro Manila (CNN Philippines, September 6) — Maritime experts warned of “dangers” in the Philippines’ pronouncement it is now on China’s side in seeking a revision of the United Nations Convention on the Law of the Sea (UNCLOS).

While Manila and Beijing may agree on the need for foreign vessels to seek permission to pass through another country’s waters, a Washington-based think tank said this is just part of the “vast” provisions China wants changed.

“[T]heir differences on the treaty are much larger and represent a clear threat to Philippine interests,” Gregory Poling, director of the Asia Maritime Transparency Initiative that monitors the South China Sea dispute, told CNN Philippines in an e-mail.

“China wants to expand the definition of historic waters and historic rights to allow it to claim special rights throughout the South China Sea. This would effectively make the Philippines’ exclusive economic zone no longer exclusive—it would have to share its resources with China,” Poling explained.

China insists on its sweeping claim to almost the entire South China Sea based on a historical nine-dash line, which the 2016 arbitral ruling invalidated. Beijing rejects the decision. The landmark ruling by a tribunal in The Hague recognized the Philippines’ sovereign rights to areas within its 200-nautical mile exclusive economic zone in the South China Sea that Beijing is claiming. The government calls this West Philippine Sea where China built artificial islands, blocked Filipino fishermen from fishing, and interfered in petroleum exploration.

READ: What you need to know about the arbitral tribunal's ruling

Also among the provisions Beijing could seek to revise, Poling said, is Article 121 of the UNCLOS, which states that uninhabitable rocks shall have no exclusive economic zone or continental shelf. This was the provision the Philippines used to debunk China’s claims to Mabini (Johnson), Calderon (Cuarteron) and Kagitingan (Fiery Cross) Reefs in the Spratlys. China claims the whole of the Spratlys or Nansha Islands as part of its territorial sea, exclusive economic zone, and continental shelf.

Poling said the Philippines and China cannot pick a single issue – prior notification of foreign vessels – and then seek to revise the entire treaty. "Picking one single issue on which the two sides agree is missing the forest for the trees."

Aligning with China

Foreign Affairs Secretary Tedoro “Teddy Boy” Locsin, Jr. on Wednesday declared that the Philippines is “now on the side of China in the revision of UNCLOS.” This follows China’s agreement to seek permission to pass through Philippine waters, as demanded by President Rodrigo Duterte. The President’s statement was made in the wake of government protests on the presence of Chinese warships and survey vessels in the country’s waters this year.

Renato De Castro, a professor at the International Studies Department of the De La Salle University in Manila, said this is the first time that the Philippines expressed intent to seek UNCLOS’ revision.

“The Philippines has, in a way, been at the fence in the past,” De Castro said in a phone interview.

He stressed, however, that by aligning with the Chinese position on prior notification of foreign vessels, Manila risks “antagonizing the US and its allies,” which believe that the right of innocent passage should be absolute.

READ: Duterte can't ban foreign ships from passing PH

Poling likewise said it is “a minority position and would be unlikely to gain much international support.”

The US, a longstanding military ally of the Philippines, does not claim any part of the South China Sea, but conducts freedom of navigation operations and calls out China's alleged militarization of contested areas.

Poling and De Castro agreed the UNCLOS is not likely to be revised because of little support from other countries. The Philippines and China signed the UNCLOS in 1982 and 1994, respectively. The Philippines cited UNCLOS in its arbitration case against China's claims to vast sections of the South China Sea.