HONG KONG (AP) — The Chinese military said Monday said it was dispatching air, navy and rocket troops to conduct joint military drills around Taiwan, a move it called a “stern warning” against separatist and “external interference” forces.

The drills came after Beijing expressed anger at U.S. arms sales to the territory and a st atement by Japan’s prime minister, Sanae Takaichi, saying that its military could get involved if China were to take action against Taiwan, the self-governing island that the world’s second-biggest economy says must come under its rule. But the Chinese military did not mention Japan in its statement on Monday morning.

China and Taiwan have been governed separately since 1949, when a civil war brought the Communist Party to power in Beijing. Defeated Nationalist Party forces fled to Taiwan. The island has operated since then with its own government, though the mainland’s government claims it as sovereign territory.

Senior Col. Shi Yi, spokesperson of the People's Liberation Army's Eastern Theater Command, said the drills, code-named “Justice Mission 2025," would be conducted in the Taiwan Straits and areas to the north, southwest, southeast and east of the island. Shi said the activities will focus on sea-air combat readiness patrol, “joint seizure of comprehensive superiority,” blockades on key ports and deterrence outside the island chain.

“It is a stern warning against ‘Taiwan independence’ separatist forces, and it is a legitimate and necessary action to safeguard China’s sovereignty and national unity,” the command said in a statement released on WeChat.

Beijing last week also imposed sanctions against 20 U.S. defense-related companies and 10 executives, a week after Washington announced large-scale arms sales to Taiwan valued at more than $10 billion. If approved by the U.S. Congress, it would be the largest-ever American weapons package to the self-ruled territory.