China said on Tuesday it will conduct military exercises in the South China Sea this week, just days after complaining that a U.S. aircraft carrier group had sailed through the disputed waters.

A notice issued by the country’s Maritime Safety Administration prohibited entry into a portion of waters in the Gulf of Tonkin to the west of the Leizhou Peninsula in southwestern China from January 27 to January 30, but did not include details on when the drills would take place or on their scale, al Jazeera reported. 

The USS Theodore Roosevelt led a group of ships into the South China Sea on Saturday to promote “freedom of the seas,” the U.S. military said, days after Joe Biden began his term as president.

China claims sovereignty over the entire sea based on its historic “nine-dash line” and has been increasingly assertive in recent years, building military bases on rocky outcrops and deploying its coastguard and maritime militia. The waters are also claimed by the littoral states – Vietnam, Malaysia, the Philippines, and Brunei – as well as Taiwan – and have become another flashpoint in the testy bilateral relationship between Beijing and Washington as the U.S. military has stepped up activities in the sea.

China on Monday complained that U.S. action to “flex its muscles” was not conducive to peace and stability in the region.

Meanwhile, Chinese President Xi Jinping has warned global leaders against starting a “new Cold War” and urged unity in the face of the coronavirus pandemic.

“To build small cliques or start a new Cold War, to reject, threaten or intimidate others … will only push the world into division,” said Xi at an all-virtual Davos forum on Monday.

The words appeared to be aimed at U.S. President Joe Biden’s plans to revitalize global alliances to counter China’s growing influence. Biden, busy handling several urgent domestic crises, did not participate at Davos and tasked U.S. climate envoy John Kerry with representing Washington.

In a swipe at moves targeting China launched by the previous U.S. administration under Donald Trump, Xi said the confrontation “will always end up harming every nation’s interests and sacrificing people’s welfare”.

Xi, making his first appearance at the forum since his vigorous defence of free trade and globalization in an address in Davos in 2017, advocated multilateralism as the way out of current challenges in a roughly 25-minute speech.