China’s foreign ministry on Sunday expressed strong disapproval of a brief visit to the United States by Taiwan Vice President William Lai. They labeled him as a separatist and a “troublemaker.” Beijing vowed to take decisive actions to protect its sovereignty.

Lai, who is the leading candidate for Taiwan’s upcoming presidential elections in January, arrived in New York on Saturday. The purpose of his visit is officially a transit on his way to Paraguay for the inauguration of its president.

China, which considers Taiwan as its own territory, has repeatedly criticized Lai’s trip. He plans to make another stopover in San Francisco on his return to Taipei.

In a statement released after Lai’s arrival in New York, China’s foreign ministry expressed opposition to any visits by “Taiwan independence separatists” to the United States. They labeled Lai as someone who stubbornly supports Taiwan independence and creates trouble.

According to the ministry, Taiwan is of utmost importance to China, and it believes that tensions in the Taiwan Strait have risen due to Taiwan’s attempts to seek independence with the support of the United States. China stated that it will closely monitor the situation and take strong measures to defend its national sovereignty and territorial integrity.

China particularly dislikes Lai, who has previously identified himself as a proponent of Taiwan independence. However, Lai has repeatedly emphasized during his campaign that he does not intend to change the current status quo and that the future of Taiwan should be decided by its people.

According to a source familiar with the trip, Lai will participate in receptions with overseas Taiwanese during his stopover in New York, where he will deliver a speech.

The source also mentioned that Lai will not meet with U.S. lawmakers and that he intends to keep the visit “low key” in accordance with the shared position of Taipei and Washington to manage risks while dealing with an authoritarian region during this sensitive time.

Upon arriving at his New York hotel, Lai was greeted by supporters waving flags. He expressed excitement about seeing friends and participating in transit programs in New York on his social media platform.

Laura Rosenberger, chair of the American Institute in Taiwan (AIT), a U.S. government-run non-profit organization responsible for unofficial relations with Taiwan, stated that she plans to meet Lai in San Francisco during his return journey.

Taiwanese officials believe that China is likely to conduct military drills near Taiwan this week, using Lai’s U.S. stopovers as an excuse to intimidate voters before next year’s election and instill fear of war.

On Sunday, China’s People’s Liberation Army Eastern Theatre Command, responsible for the Taiwan area, posted a video on its WeChat account showing fighter jets engaged in practice dog fights. The command stated that its forces have recently participated in high-intensity flight training.

Lai’s visits coincide with efforts by Beijing and Washington to improve relations, including a possible visit to the U.S. by Chinese Foreign Minister Wang Yi, which could pave the way for a meeting between U.S. President Joe Biden and Chinese leader Xi Jinping this year.

In the past three years, China has increased its military activities around Taiwan in an attempt to pressure the island into accepting Beijing’s sovereignty. In April, China conducted war games near Taiwan in response to Taiwan President Tsai Ing-wen’s meeting with U.S. House Speaker Kevin McCarthy in California during her return trip from Central America.