The patrol comes less than a week after Philippine President Ferdinand Marcos Jnr signed the Maritime Zones Act and Archipelagic Sea Lanes Act, embedding Manila’s claims to the South China Sea in domestic law. The US expressed its support for the Philippine legislation, saying other countries had passed similar laws.

China has held sea and air combat drills at disputed Scarborough Shoal, an uninhabited area of reefs and rocks it had seized from the Philippines in the South China Sea.

The Philippines has protested China’s baselines around the disputed Scarborough Shoal, as tensions between the two nations build up anew over their competing claims in the South China Sea.

China declared its maritime baselines around Scarborough Shoal after the Philippines passed laws defining its maritime zones and sea lanes last week.

The Philippines has explicitly labeled China's baseline declarations around Scarborough Shoal (Bajo de Masinloc) as illegal under international law — a direct pushback against Beijing after it aired its fury over Manila's new maritime zones law.