The U.S. and Philippine Coast Guards held a joint passing exercise as China's 'monster ship' lurked near a Philippine island.

Footage shows the treaty allies simulating search-and-rescue operations and medical evacuations off the Philippines' Lubang Island in Occidental Mindoro province on July 16.

Philippine Coast Guard (PCG) spokesman Commodore Jay Tarriela said the drills involved the PCG's BRP Melchora Aquino (MRRV 9702) and the US Coast Guard's (USCG) Cutter Waesche (WMSL-751).

He said in a statement: 'Sharing similar mandates, values, and objectives of protecting lives at sea and maintaining a rules-based maritime order, this exercise highlights the closer and expanding relations between the Coast Guards of the two allied nations.

'The exercise aims to strengthen maritime cooperation and interoperability between the two Coast Guard services in the areas of maritime safety and environmental protection.'

The PCG also said that China Coast Guard (CCG) vessel 5303 was spotted approaching some 60 nautical miles off the Philippine and American ships during the passing exercise.

It was reported to have left the area to head for the Philippines' Palawan island, close to where the Chinese 'monster ship' CCG 5901 was anchored in Escoda Shoal.

Expansionist China currently lays claim over almost the entire South China Sea, one of the world's busiest sea lanes. But a United Nations-backed tribunal in 2016 deemed its claims groundless.

The Communist rogue state - accused of genocide for its crimes against the Uyghur population - has been steadily increasing its influence in recent years through investment in developing countries.