Carrier strike groups Theodore Roosevelt and Nimitz carried out multiple manoeuvres in the busy resource-rich waterway.
The presence of Chinese vessels at a disputed reef off the Philippines could ignite “unwanted hostilities”, a top aide to President Rodrigo Duterte has warned, intensifying a diplomatic spat over the ships that Manila described as “maritime militia”.
More than 200 Chinese boats were first spotted on March 7 at Whitsun Reef, approximately 320 kilometres (175 nautical miles) west of Palawan Island within the Philippines’s exclusive economic zone (EEZ).
Most of them have since scattered across the Spratly Islands but last week dozens of the Chinese-flagged vessels were still anchored at the boomerang-shaped reef, according to Philippine military patrols.
For weeks Manila has called on Beijing to withdraw the “maritime militia” vessels, saying their incursion into the Philippines’s EEZ is illegal as defined by the International Court of Arbitration at The Hague.
But China – which claims almost the entirety of the resource-rich sea – has refused, insisting they are fishing boats sheltering from bad weather and are allowed to be there.
Duterte, who has fostered warmer ties with his superpower neighbour since taking office in 2016, has expressed concern to the Chinese ambassador over the ships, according to his spokesman.
Until Monday he had left the tough-talking in public to his defence and foreign ministers.
But in the strongest remarks yet from his office, Duterte’s top legal counsel Salvador Panelo warned China’s “present territorial incursions is producing an unwelcome stain in their bond and may trigger unwanted hostilities that both countries would rather not pursue.”
“The matter of territorial dispute has to be resolved in the diplomatic negotiating table or by the dictates of international law,” Panelo said in a statement on Monday.
It comes a day after outspoken Defence Secretary Delfin Lorenzana accused Beijing of planning to occupy more “features” in the waters – where Taiwan, Vietnam, Malaysia and Brunei also have rival claims.
“The continued presence of Chinese maritime militias in the area reveals their intent to further occupy features in the West Philippine Sea,” Lorenzana said on Sunday.
He had said earlier that he was “no fool” to believe China’s explanation adding that the boats should “get out of there.”
Beijing often invokes the so-called nine-dash line to justify its apparent historic rights over most of the South China Sea and has ignored the 2016 decision issued by The Hague that declared this assertion as without basis.
The Philippine foreign ministry, which has already lodged a diplomatic protest over the ships, pledged Monday to send a complaint “for every day” Beijing delays pulling out the vessels.
It said the boats “blatantly infringe” on Philippine jurisdiction.
In an apparent reference to China’s donation of COVID-19 vaccines, Panelo said the Philippines appreciated the “humanitarian gesture”.
But he added: “We will not be blinded however by any act done by it in violation of international law and in derogation of our sovereign rights.”
Duterte’s spokesman Harry Roque echoed on Monday the view and told a news conference: “We will not give up even a single inch of our national territory or our exclusive economic zone (EEZ).”
Roque said later said on Tuesday that the president wants to resolve the issues through “diplomatic channel” and through peaceful means.
China’s embassy in Manila did not immediately respond to a request for comment.
In an earlier response to the Philippines’s defence chief, it said that he should avoid making “wanton remarks.”
“The Chinese Embassy has taken note of the perplexing statement by Philippine Defense Secretary on Chinese fishing vessels around Niu’e Jiao in the South China Sea,” the Chinese embassy in Manila said in a statement, referring to the reef by its Chinese name.
It said that the reef was part of China’s Nansha Islands and a “traditional fishing ground” for Chinese fishermen for “many years.”