China claims almost the entire South China Sea, including waters and islands near the shores of its neighbours, and has ignored an international tribunal ruling that its assertions have no legal basis.
It deploys boats to patrol the busy waterway and has built artificial islands that it has militarised to reinforce its claims.
Miller said the tribunal’s 2016 decision “is final and legally binding on the PRC and the Philippines”.
The US “calls upon the PRC to abide by the ruling and desist from its dangerous and destabilising conduct”, he added, using an acronym for the People’s Republic of China.
“The United States stands with our Philippine allies in the face of these dangerous and unlawful actions,” he said, adding that a mutual defence treaty between the US and Philippines “extends to armed attacks on Philippine armed forces, public vessels or aircraft – including those of its Coast Guard – anywhere in the South China Sea”.
The Philippines said one of its boats was “rammed” by China during the incident on Sunday. China’s coast guard, however, accused the Philippine boat of “deliberately colliding” with the Chinese vessel after disregarding “multiple stern warnings”.
Relations between Manila and Beijing have deteriorated under President Ferdinand Marcos, who has sought to improve ties with traditional ally Washington and push back against Chinese actions in the South China Sea.