"China can and should have a cooperative relationship with the rest of the region ... But behaviour that erodes other nations' sovereignty and sows distrust of China's intentions must end," acting US Secretary of Defense Patrick Shanahan told a regional security forum in Singapore.

"Until it does, we stand against a myopic, narrow, and parochial vision of the future, and we stand for the free and open order that has benefitted us all, including China."

Shanahan said the United States was investing heavily in the Indo-Pacific region to maintain its military superiority and capability to defend its Asian allies.

Washington and Beijing have been vying for influence in the region which hosts potential flashpoints such as the South China Sea, Korean Peninsula and the Taiwan Strait.

Ties between the two powers are expected to take centre stage at the Singapore conference which gathers defence ministers and top military officials from around the world.

For the first time since 2011, China has sent its defence minister to the gathering.

"When we talk about preparedness, we mean having the right capabilities in the right places to respond to crises, and to compete with and deter high-end adversaries," the Pentagon chief said.

While the United States does not seek conflict, it knows that having the capability to win wars is the best deterrence, he said.

"We want to ensure no adversary believes it can successfully achieve political objectives through military force," he said.