The Philippines formally notified China today that it is seeking international arbitration to declare Beijing's claims in the potentially oil-rich South China Sea "illegal and invalid."
Foreign Secretary Albert del Rosario said that his department had summoned Chinese ambassador Ma Keqing and handed her a note notifying the Chinese government that the Philippines is referring both countries' conflicting claims to an international tribunal.
Several countries claim parts of the South China Sea.
China has confronted Filippino ships in a stand-off over the Scarborough Shoal, which both countries claim.
The Philippines withdrew ships from the shoal last June under protest.
The Philippines says that arbitration through a tribunal operating under the 1982 UN convention on the law of the sea could lead to a decision that would direct China to respect the Philippines' claims.
But even if a tribunal ruled against China, Beijing could choose to simply ignore the ruling.
Mr Rosario said that the Philippines made the complaint after previous diplomatic efforts to resolve the territorial rifts failed.
"The Philippines has exhausted almost all political and diplomatic avenues for a peaceful negotiated settlement of its maritime disputes with China," he claimed.
The Philippines listed several aggressive moves it alleged had been launched by China in recent years to fortify its territorial claims, including the occupation of South China Sea islands and the enactment of a Chinese law to allow its patrol vessels to board foreign ships passing through waters that Beijing claims.