In Manila on Tuesday, US Secretary of State Antony Blinken unveiled what he called a "once in a generation investment" to help modernise the Philippine armed forces and coast guard.

Asked about the announcement, Beijing's foreign ministry on Wednesday warned Manila that "wooing countries from outside the region to provoke confrontation in the South China Sea will only undermine regional stability and aggravate tensions".

"Trying to introduce external forces to protect its own security will only lead to greater insecurity for itself, and it might even become someone else's pawn," spokesman Lin Jian said.

The latest high-level US visit follows a series of escalating confrontations between Philippine and Chinese vessels in the disputed waterway that have raised concern that Washington could be dragged into a conflict due to its mutual defence treaty with Manila.

The Philippines' proximity to the hotly contested South China Sea, as well as self-ruled Taiwan, would make it a key partner for the United States if a conflict were to break out in the region.

Beijing claims almost the entire waterway, despite an international ruling that its assertion has no legal basis, and considers democratic Taiwan to be part of its territory.