Philippines says it will assert its South China Sea rights

The Philippines' foreign minister said on Friday his country was determined to assert its sovereign rights in the South China Sea, at a meeting with US allies over an increasingly fraught standoff with Beijing over the waterway.

Enrique Manalo accused China of escalating what he called the harassment of the Philippines and US Defense Secretary Lloyd Austin said Washington stood with Manila against what he described as coercion.

An escalating diplomatic row and recent maritime run-ins between China and the Philippines, a US treaty ally, have made the highly strategic South China Sea a potential flashpoint between Washington and Beijing.

The officials spoke at a meeting between US and Philippines defence and foreign secretaries and their national security advisers, a day after the leaders of the US, Japan and the Philippines met at the White House over the issue.

"We are determined to assert our sovereign rights, especially within our economic - exclusive economic zone," Manalo said.

He added that he hoped the meeting with US officials would allow Washington and the Philippines to better coordinate their responses on the diplomatic and defence and security fronts to actions in the South China Sea.

Austin said the US commitment to its mutual defence treaty with the Philippines was "ironclad".

"We're working in lockstep with our colleagues at the (Philippines) Department of National Defence to strengthen interoperability between our forces, to expand our operational coordination and to stand up to coercion in the South China Sea," he said.

Earlier on Friday, China summoned Japanese and Philippine diplomats to express dissatisfaction over negative comments about it aired during the White House summit, the foreign ministry in Beijing said.

At summits this week in Washington, the allied leaders unveiling a wide range of pacts to boost security and economic ties.