Filipino fishing crews reported seeing the large ship near Scarborough Shoal and said planes were landing and taking off from the vessel.
The US military refused to confirm the Wasp’s movements, saying it would compromise “force protection and security”. A spokeswoman said the Wasp “has been training with the Philippine navy ships in Subic Bay and in international waters of the South China Sea … for several days”.
The Philippines’ Foreign Affairs Secretary Teodoro Locsin said the US would remain the “only military ally” of Manila amid reports of an increased Chinese presence in the South China Sea.
A flotilla of Chinese vessels which has been almost stationary near the island of Pag-asa or Thitu since January has sparked complaints from the Philippine military.
“The US is and will remain our only military ally. You can’t make an ally out of a near power: too close for comfort. Natural allies are the US across the Pacific and Russia behind China,” Locsin tweeted.
“With China, friendship is wisest; never a military alliance. The logic of balance of power,” he added.
To complicate matters further, two Russian destroyers and a tanker have docked in the Philippines for a “goodwill visit”.
The Admiral Tributs and Vinogradov, classified as “large, anti-submarine ships”, docked in Manila along with the Admiral Irkut sea tanker, according to the Philippine News Agency.
In January, three Russian vessels docked in Manila to “further enhance and sustain the promotion of peace, stability and maritime cooperation”.
Scarborough Shoal, claimed by the Philippines, China and Taiwan, is one of the South China Sea’s strategic hotspots.
It was seized by China in 2012 after a prolonged standoff with the Philippines and the Chinese navy then blocked off the lagoon.
Scarborough Shoal is a key strategic target for Beijing, forming a large “strategic triangle” comprising Woody Island in the Paracel Islands to the northwest and Spratly strongholds to the south. It would give the Chinese military radar, missile and air coverage and the ability to enforce an air-defence identification zone (ADIZ) across the resource-rich sea.
In January 2018, the US Navy sent a guided-missile destroyer about 22km from the Scarboroughs during one of its “freedom of navigation operations” in the South China Sea.
The US says the web of Chinese artificial islands could restrict free maritime movement.
The USS Wasp amphibious assault vessel. Picture credit: US Seventh Fleet