A cooperation agreement by the Philippines, the United States and Japan will change the dynamic in the South China Sea and the region, the Philippine president has said, while seeking to assure China it was not a target.

“I think the trilateral agreement is extremely important,” Ferdinand Marcos Jr told a press conference in Washington on Friday, a day after meeting President Joe Biden and the Japanese prime minister, Fumio Kishida, in the nations’ first trilateral summit.

"It is going to change the dynamic, the dynamic that we see in the region, in Asean in Asia, around the South China Sea,” Marcos said, referring to the Association of Southeast Asian Nations.

The three leaders expressed “serious concerns” about China’s “dangerous and aggressive behaviour” in the South China Sea, a conduit for more than $3tn of annual ship-borne commerce, with various maritime disputes between China and other countries.