A highly anticipated defense forum in Singapore kicked off with a friendly handshake between Pentagon chief Lloyd Austin and Chinese Defense Minister Li Shangfu. It ended Sunday with few other signs of optimism that the world’s biggest economies could avoid an eventual collision.

Austin used his speech at the Shangri-la Dialogue to chide China over its refusal to meet unless the U.S. lifted sanctions on Li, saying that “a cordial handshake over dinner is no substitute for a substantive engagement.” The remarks came as a Chinese vessel harassed an American warship transiting the Taiwan Strait, drawing attention to the biggest potential military flashpoint between the two powers.

Li fired back on Sunday, accusing “some big power” of creating divisive alliances, bullying other nations, spurring an arms race and seeking to contain China with its support for Taiwan. China’s military “will not hesitate for a second” to move on Taiwan if necessary, he said, while dismissing questions about near-collisions in disputed waters. Competing militaries should stay away and “mind your own business,” Li said.

Other countries at the event, meanwhile, repeatedly spoke of the dangers posed by rising Us-china tensions and the need to prevent anything like Russia’s war in Ukraine from occurring in Asia.

“There was a real sincerity and urgency that what happened in Ukraine must not happen in Asia,” Singapore Defense Minister Ng Eng Hen told reporters after a lunch that included all of the most senior defense officials at the event. “Many ministers have said if you have a simultaneous war in Europe and Asia it’s catastrophic globally.”

The back-and-forth between the U.S. and China at the annual Shangri-la Dialogue was always expected to be fraught, particularly after President Joe Biden’s administration declined to remove sanctions placed on Li in 2018 over his role in purchasing a Russian missile defense system. It was also the first major defense forum since then-house Speaker Nancy Pelosi’s visit to Taiwan in August prompted China to conduct unprecedented military exercises surrounding the island.