The de facto U.S. ambassador to Taiwan on Friday expressed concern that Beijing is attempting to influence the island’s coming elections, days after China sent its first domestically built aircraft carrier through the Taiwan Strait.

Beijing confirmed earlier in the week that the carrier had traversed the strait separating China from self-ruled Taiwan, saying it was “routine” training.

“We of course regard any of these threatening actions with concern,” said Brent Christensen, the director of the American Institute in Taiwan, when asked to comment on the sailing.

AIT serves as America’s de facto embassy in Taiwan.

The United States switched diplomatic recognition from Taiwan to China in 1979 but has remained an important ally — and arms supplier — to Taipei.

“As to the elections, of course we are aware that China is attempting to apply pressure through various means on Taiwan. Certainly these attempts to influence Taiwan’s democratic process are our concerns,” he added.

China’s sail-by comes as Taiwan gears up for elections in January, with Beijing-skeptic President Tsai Ing-wen seeking a second term against a challenger who favors warmer ties with China.

Friday marked the close of registration of candidates for the presidential and legislative elections. Tsai will be running against Han Kuo-yu of the Kuomintang, the main opposition party, and James Soong, leader of the People First Party, a KMT splinter party. Tsai has been leading Han in recent public opinion polls, with Soong trailing far behind.

Taiwan’s single-house legislature has 113 seats. In the 2016 elections, Tsai’s DPP picked up 68 seats, far more than the KMT’s 35. The DPP-led coalition had 73 seats, while the KMT and its allies could marshal only 39.

Christensen said Washington views any efforts to determine Taiwan’s future by anything other than peaceful means as “a threat to peace and security in the Western Pacific.”

Foreign Minister Joseph Wu tweeted on Sunday that China “intends to intervene” in Taiwan’s elections,” adding, “Voters won’t be intimidated!”

Taiwan’s Defense Ministry said it had dispatched ships and planes to track and closely monitor the carrier’s movements, and that U.S. and Japanese vessels trailed it in the waterway separating the island from mainland China.

Beijing has stepped up military and diplomatic pressure on Taiwan since Tsai came to power in 2016. Her government refuses to acknowledge its view that the self-ruled, democratic island is part of “one China.”

Tsai — who has voiced support for Hong Kong’s pro-democracy movement — has described the elections as a fight for Taiwan’s freedom and democracy.

China still sees Taiwan as part of its territory awaiting reunification, by force if necessary.