The US and China have deployed aircraft carriers into the East and South China Seas, as the two superpowers engage in their latest powerplays on the disputed waters.
It comes amid already high tensions in the Indo-Pacific region, with hundreds of Chinese vessels, which the Philippines claim are linked to China’s navy, moored inside Manila’s 320-kilometre exclusive zone.
Last week the Philippines sent light military aircraft to fly over the 200-plus boat flotilla, at the Whitsun Reef.
Despite Manila’s growing protest, the Chinese fleet remains.
The US, Japan and Indonesia also stepped up pressure on China over the dispute last week.
On Sunday, according to local media, a US aircraft carrier strike group led by the USS Theodore Roosevelt entered the South China Sea from the Strait of Malacca.
The USS Mustin guided-missile destroyer is also sailing in the East China Sea, according to the Beijing-based South China Sea Strategic Situation Probing Initiative.
The Chinese aircraft carrier, Liaoning, passed through the Miyako Strait off southwestern Japan on the weekend.
China has claimed almost all of the South China Sea, and since 2014 has built up tiny reefs and sandbars into man-made artificial islands heavily fortified with missiles, runways and weapons systems – prompting outcry from the other governments.
At least six other governments also have overlapping territorial claims in the contested waterway: the Philippines, Vietnam, Malaysia, Indonesia, Brunei and Taiwan.
Trade shipments worth trillions of dollars pass through the South China Sea every year.
Last week the Royal Australian Navy took part in US-led military exercises in the eastern Pacific.
The US also conducted exercises with Japan in the East China Sea and India in the Indian Ocean.