US Secretary of State Marco Rubio reaffirmed Washington's commitment to Manila and condemned Beijing for its "dangerous and destabilising" actions in the Sea, in his first phone call with Philippine Foreign Secretary Enrique Manalo.

The Philippines will soon decide on an international platform to sue China for alleged damage to the marine environment, its justice minister said, as it pursues a second high-profile legal challenge against Beijing over the South China Sea.

The United States is not a party to the issue of the South China Sea and has no right to interfere in maritime issues between China and the Philippines, Foreign Ministry spokeswoman Mao Ning said on Thursday after Washington and Manila made unwarranted remarks against Beijing.

Beijing and Manila have agreed to continue talks on settling their territorial differences despite Philippine protests about the presence of a Chinese "monster ship" near the contested Scarborough Shoal.

Officials from the Philippines and China have held talks on the disputed South China Sea. Manila expressed "serious concern" over Beijing's deployment of its largest coast guard ship in Philippine waters.