China has dispatched a naval group led by an aircraft carrier to the western Pacific Ocean following the United States’ deployment of ship-sinking missiles in the Philippines, warning the US and its South China Sea allies that it is ready for further encounters at sea and in the air.

The Philippine navy confirmed on Thursday that a pair of Chinese naval ships was spotted near the country, including the Shandong and the CNS Tianguanxing electronic surveillance ship.

On the other hand, the US Navy aircraft carrier USS Nimitz, which left the island of Guam on Monday after a port visit, was underway in the Philippine Sea as of Wednesday.

On Monday, the US and its allies in the western Pacific Ocean kicked off the Balikatan military exercises in the region. The significance of the 40th iteration of the annual drills is the deployment of advanced US military systems.

As part of the exercises, the US has unprecedentedly deployed the Navy Marine Expeditionary Ship Interdiction System (NMESIS) to the Luzon Strait — a chokepoint for Chinese naval access to the Pacific Ocean north of the Philippines.

Analysts view the move as simulating a potential blockade of the Bashi Channel in the Luzon Strait in the event of an encounter in the Taiwan Strait.

China’s Ministry of National Defense on Thursday warned the Philippines and other South China Sea countries against colluding with the United States and other external powers to stir up tensions.

“Military cooperation between countries should not target or harm the interests of any third party, nor should it undermine regional peace and stability,” ministry spokesman Senior Colonel Zhang Xiaogang said. 

While calling for the South China Sea to remain “a sea of peace, cooperation and friendship,” he warned the Philippines to avoid undermining the common interests of countries in the region.

“The Philippines frequently conducts so-called joint patrols and exercises, and invites and deploys strategic and tactical weapons, seriously undermining the common interests of regional countries,” Zhang said.

China, he said, “firmly opposes any country strengthening military deployment in the region and provoking tensions and confrontation under the excuse of the Taiwan question.”

“Regardless of external challenges and turbulence, China will resolutely safeguard its territorial sovereignty and maritime rights and interests, and firmly maintain peace and stability in the region,” he added.

The drills are conducted as part of a US containment strategy formed by Japan, Taiwan, and the Philippines that seeks to restrict the Chinese military’s access to the Pacific Ocean and its deployment of aircraft carriers to the waters beyond the first island chain.

Around 9,000 US soldiers and 5,000 Filipino troops are participating this year in the so-called “full battle test” exercises which started on Monday.

Small contingents from Australia, Japan, Britain, France, and Canada are also participating, and 16 other countries have signed up as observers.