A cooperation agreement by the Philippines, the United States and Japan will change the dynamic in the South China Sea and the region, Philippine President Ferdinand Marcos Jr. said on Friday, while seeking to assure China it was not a target.

"I think the trilateral agreement is extremely important," Marcos told a news conference in Washington a day after meeting U.S. President Joe Biden and 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.