MANILA, Philippines (AP) — The Philippines on Thursday convened a regional meeting to study its proposal for settling a tense dispute over South China Sea islands, despite protests by China which claims the entire, potentially oil-rich area as its own.

The first such gathering is an attempt by the Philippines, which together with Vietnam has been the most vocal party in the dispute, to present a unified regional policy in confronting China’s exclusive claim over all the islands.

The meeting is limited to maritime and legal experts from the 10-member Association of Southeast Asian Nations, while China prefers bilateral negotiations with each claimant country.

Two senior Philippine diplomats told The Associated Press that Beijing had protested the two-day meeting. Beijing has also questioned why ASEAN should deal with the disputes as a group when the majority of its members are not claimants, the two diplomats said, speaking on condition of anonymity because they were not authorized to talk to reporters.

Only four ASEAN countries — Brunei, Malaysia, the Philippines and Vietnam — lay claims to the region believed to be rich in oil. The other claimants are longtime rivals China and Taiwan.

The dispute is so entrenched that claimant countries can’t even agree on the names of the islands and surrounding waters. Philippines calls South China Sea the West Philippine Sea.

Resolving the dispute “may take centuries,” acknowledged Philippine Vice President Jejomar Binay while talking to reporters after delivering an opening speech to the delegates at the conference.

He noted in the speech that the sea — through which more than half of the world’s supertankers pass — has “become a source of tension, which threatens the security” of not only the vital sea lane but also the region and the world.

The Philippine proposal being discussed includes delineating the disputed islands so claimants could demilitarize and turn them into a “zone of peace, freedom, friendship and cooperation.”

The Philippines says that not the entire South China Sea is disputed, but only the Spratly archipelago, which is sought by all six claimants, and the Paracel Islands, which are being contested by China, Vietnam and Taiwan.

Once the disputed areas are delineated, claimants can decide to withdraw their troops, replace them with civilian forces and undertake joint research projects and disaster drills to boost trust.

However, segregating the disputed areas would be tough. The Philippines, for example, claims as its own a potentially gas-rich area called the Reed Bank, which lies off its western province of Palawan.

China, however, contests that claim, and two Chinese patrol boats tried to drive away a Philippine oil exploration ship from the area in March. The Philippines protested the incident as one of several intrusions by China into its territorial waters that reignited tensions in the first half of the year.