China’s military declared Monday it is “ready to fight” after completing three days of large-scale combat exercises around Taiwan that simulated sealing off the island in response to the Taiwanese president’s trip to the U.S. last week.

The “combat readiness patrols” named Joint Sword were meant as a warning to self-governing Taiwan, which China claims as its own, China’s military said earlier.

“The theater’s troops are ready to fight at all times and can fight at any time to resolutely smash any form of ‘Taiwan independence’ and foreign interference attempts,” it said Monday.

The exercises were similar to ones conducted by China last August, when it launched missile strikes on targets in the seas around Taiwan in retaliation for then-Speaker Nancy Pelosi’s visit to Taiwan, but have been smaller and less disruptive.

Military experts say the exercises serve both as intimidation and as an opportunity for Chinese troops to practice sealing off Taiwan by blocking sea and air traffic, an important strategic option the Chinese military might pursue in the event it uses military force to take Taiwan.

The Chinese actions follow President Tsai Ing-wen’s delicate mission to shore up Taiwan’s dwindling diplomatic alliances in Central America and boost its U.S. support, a trip capped with a sensitive meeting with U.S. House Speaker Kevin McCarthy in California. A U.S. congressional delegation also met with Tsai over the weekend in Taiwan after she returned.

China responded immediately to the McCarthy meeting by imposing a travel ban and financial sanctions against those associated with Tsai’s U.S. trip and with increased military activity through the weekend.

“China wants to use any increase of diplomatic interactions between the U.S. and Taiwan as an excuse to train its military,” said Kuo Yu-jen, a defense studies expert and director of the Institute for National Policy Research in Taiwan.

Beijing says contact between foreign officials and the island’s democratic government encourages Taiwanese who want formal independence, a step China’s ruling Communist Party says would lead to war. The sides split in 1949 after a civil war, and the Communist Party says the island is obliged to rejoin the mainland, by force if necessary.

After Pelosi visited Taiwan, China conducted missiles strikes on targets in the seas around Taiwan, while also sending warships and war planes over the median line of the Taiwan Strait. It also fired missiles over the island itself which landed in Japan’s exclusive economic zone, in a significant escalation.

The live-fire exercises disrupted flights and shipping in one of the busiest shipping lanes for global trade. This time, shipping and maritime traffic have largely continued as normal, Kuo said.

Exercise Focused on Air Power

The exercises this time have focused more on air strength, with Taiwan reporting 200 flights by Chinese warplanes in the past three days. Chinese state broadcaster CCTV, citing the People’s Liberation Army, said the exercises are “simulating the joint sealing off” of Taiwan as well as “waves of simulated strikes” at important targets on the island.

On Monday, the PLA said its Shandong aircraft carrier was taking part in the exercises encircling Taiwan for the first time. It showed a video of a fighter jet taking off the deck of the ship in a post on Weibo, the social media platform.

The appearance of the Shandong aircraft carrier in the Pacific Ocean suggests that it could be used to prevent foreign militaries from coming to help Taiwan, said Han Gan-ming, a research fellow at the government-backed Institute for National Defense and Security Research.

“In the future if there’s a similar military maneuver, then Taiwan will have to face it alone,” Han said.

Between 6 a.m. Sunday and 6 a.m. Monday, a total of 70 planes were detected and half crossed the median of the Taiwan Strait, an unofficial boundary once tacitly accepted by both sides, according to Taiwan’s Ministry of National Defense. Among the planes that crossed the median were eight J-16 fighter jets, four J-1 fighters, eight Su-30 fighters and reconnaissance planes. Taiwan also tracked J-15 fighter jets, which are paired with the Shandong aircraft carrier.

Later Monday morning, Taiwan’s defense ministry reported another 59 flights by bombers, as well as multiple fighter jets.

That followed a full day between Friday and Saturday in which eight warships and 71 planes were detected near Taiwan, according to the island’s Defense Ministry. It said in a statement that it was approaching the situation from the perspective of “not escalating conflict, and not causing disputes.”

Taiwan said it monitored the Chinese moves through its land-based missile systems, as well as from its own navy vessels.

China’s military harassment of Taiwan has intensified in recent years with planes or ships sent toward the island on a near-daily basis, with the numbers rising in reaction to sensitive activities. The military activity has increased a notch since Pelosi’s visit, with Chinese PLA fighter jets regularly flying over the middle boundary line. Experts say PLA navy vessels regularly navigate the waters off Taiwan’s northeastern coast.

Meanwhile, to the south in the South China Sea, the U.S. 7th Fleet said its missile destroyer USS Milius sailed by Mischief Reef in a freedom of navigation operation. China has built an artificial island on the sea feature to stake its claim to the disputed territory.

China said the U.S. “illegally trespassed” into waters near the reef without the permission of the Chinese government, according to a statement from the Chinese military’s southern command.

Outside of the military maneuvers, Kuo said he was worried about the announcements from Fujian’s Maritime Safety Administration from last week, when it said it would conduct “on-site inspections” of cargo ships and working vessels in the Taiwan Strait as part of a patrol exercise.

“First they’ll target ships traveling between the Strait, then they will target any international ship,” he said. “Gradually this will become the de facto new status quo.”

One of the U.S. representatives who attended the meeting with Tsai last week said Saturday the U.S. must take seriously the threat China poses to Taiwan. Republican Mike Gallagher, chairman of the U.S. House Select Committee on China, told The Associated Press that he plans to lead his committee in working to shore up the island government’s defenses, encouraging Congress to expedite military aid to Taiwan.