HONG KONG (AP) — China’s military on Monday dispatched air, navy and missile units to conduct joint live-fire drills around the island of Taiwan, which Beijing called a “stern warning” against separatist and “external interference” forces.

Taiwan’s aviation authority said more than 100,000 international air travelers would be affected by flight cancellations or diversions.

The drills came after Beijing expressed anger at what could be the largest-ever U.S. arms sale to the self-ruled territory, and at a statement by Japan’s prime minister, Sanae Takaichi, saying its military could get involved if China takes action against Taiwan. China says Taiwan must come under its rule.

China’s military did not mention the United States and Japan in its statement on Monday, but Beijing’s foreign ministry accused Taiwan’s ruling party of trying to seek independence through requesting U.S. support.

Taiwan’s Defense Ministry said rapid response exercises were underway, with forces on high alert. “The Chinese Communist Party’s targeted military exercises further confirm its nature as an aggressor and the biggest destroyer of peace,” it said.

U.S. President Donald Trump on Monday said he was not informed of the military exercise in advance but that he was not worried either, because China has been “doing naval exercises for 20 years in that area.”

Touting his “great relationship” with Chinese President Xi Jinping, Trump suggested he didn’t think Xi was going to attack Taiwan.

Beijing sends warplanes and navy vessels toward the island on a near-daily basis, and in recent years it has stepped up the scope and scale of the exercises.

Senior Col. Shi Yi, spokesperson of China’s People’s Liberation Army’s Eastern Theater Command, said the drills would be conducted in the Taiwan Strait and areas to the north, southwest, southeast and east of the island.