BEIJING — Growing trade tensions between the U.S. and China are starting to mar other aspects of their bilateral ties, with the Chinese government canceling high-level security talks with U.S. Defense Secretary James Mattis.

The diplomatic and security dialogue had been planned for October. Mattis was to visit China for the meeting, but the trip is now off, and that it is unclear if it will be rescheduled, a senior U.S. official told the New York Times, which first reported the cancellation.

Cooling relations between the two countries were apparent even at a Thursday reception to celebrate China’s founding day at the Chinese Embassy in Washington. While last year’s event drew Ivanka Trump, the eldest daughter of U.S. President Donald Trump, and her husband Jared Kushner, the highest-ranking American guest this year was Matthew Pottinger, the National Security Council’s senior director for Asia.

The number of total American attendees fell by 200 to 600.

At the event, Chinese Ambassador Ciu Tiankai signaled some concern over the situation, saying “the only right choice for us is cooperation.”

“China and the United States, permanent members of the United Nations Security Council and the world’s two largest economies, must make another historic choice on where they want this relationship to go,” he said.

But as public sentiment in China sours on the U.S., Beijing has been forced to take a stand. Before canceling the Mattis trip, China in late September postponed a dialogue between the joint chiefs of staff of each military as well as a round of trade talks.

Just last year, Trump had praised Xi as a “great leader.” Their relationship has since deteriorated, and Trump on Friday said Xi “may not be a friend of mine anymore.”

The U.S. administration is ramping up nontrade pressure on China as well. It has decided to sell parts for F-16 fighter jets and other military aircraft to Taiwan, and on Sunday sailed a Navy warship within 12 nautical miles of the Spratly Islands, a disputed chain in the South China Sea controlled by the Chinese.