China said on Wednesday it would make a “necessary response” to a planned military dialogue between the United States and Chinese-claimed Taiwan, saying it firmly opposed the event.

China has been angered by stepped up support for the democratic island by outgoing U.S. President Donald Trump’s administration, including new arms sales and visits to Taipei by senior U.S. officials, which have strained already poor Beijing-Washington ties.

The U.S. State Department said Assistant Secretary of State for Political-Military Affairs Clarke Cooper would deliver “virtual remarks” at the Taiwan political and military dialogue from the State Department late on Wednesday, though gave no other details.

Speaking in Beijing, Chinese Foreign Ministry spokeswoman Hua Chunying said it would make a “necessary response based on how the situation develops” and was “resolutely opposed” to the talks.

China urges the United States to “immediately stop any form of official exchanges and military links with Taiwan, to avoid further damaging stability in the Taiwan Strait and Sino-U.S. relations”, she added.

Taiwan’s Foreign Ministry said it would not give details of the talks, citing “Taiwan-U.S. mutual trust and a tacit diplomatic understanding”.

“The two sides often maintain close and smooth communication on various issues of common concern, so as to continue to deepen cooperation at all levels of politics, economics, and security,” said spokeswoman Joanne Ou.

Cooper met Taiwan’s top diplomat in Washington, Hsiao Bi-khim, in August, saying it was a pleasure to talk with her “as we work together for regional peace and stability”.

Democratic Taiwan, claimed by China as its sovereign territory, has come under increasing pressure from Beijing, which has ramped up military activity near the island.