A visiting US military general has used a speech in Canberra to warn that China no longer fears the United States as it used to and that this risks destabilising Asia.

General Robert Brown told an audience of high-ranking Australian defence officials and politicians that the US and its allies needed to regain a military innovation edge to deter China from starting a conflict.

General Brown, who commands US Army forces in the Pacific region, told a dinner hosted by the Australian Strategic Policy Institute that during a visit to China last year to meet top brass from the People's Liberation Army he had realised that "something was different".

"It took me a while to figure out what exactly was different in this visit,” he said. “I realised that China … for the United States, used to fear us and respect us. They don’t fear us anymore.