China's Defence Minister Wei Fenghe (centre) walks through the hotel lobby for a luncheon meeting in Singapore. Roslan Rahman/AFP

The United States warned China on Saturday against threatening its neighbours' sovereignty and said Washington is investing in new military technology 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, the Korean Peninsula and the Taiwan Strait.

Ties between the two powers are once again taking centre stage at the weekend Singapore conference known as the Shangri-La Dialogue, which gathers defence ministers and top military officials from around the world.

While the forum is purely on security, the discussions are being held against a backdrop of Sino-US trade tensions and high-tech rivalry.

US President Donald Trump. File photo

"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 the forum.

"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."

No 'fait accompli'

Washington has been pushing back against Beijing's aggressive militarisation of the South China Sea, where China has staked "indisputable" ownership over almost the whole area and rejects partial claims by Taiwan, Brunei, Malaysia, the Philippines and Vietnam.

Beijing is also regularly angered by US and other warships transiting through the Taiwan Strait, which it considers part of its territorial waters.

A French warship entered the Strait in April, prompting a warning from China's navy.

On Saturday, French minister of the armed forces Florence Parly said her country's forces will not be forced from the region.

"We will continue to sail more than twice a year in the South China Sea. There will be objections, there will be dubious maneuvers at sea. But we will not be intimidated into accepting any fait accompli," she told the forum.

This photo shows soybeans imported from Ukraine being unloaded at the port in Nantong, in China's eastern Jiangsu province. File poto/AFP

For the first time since 2011, China has sent its defence minister, General Wei Fenghe, to the Singapore gathering. Wei is scheduled to speak Sunday, when he is expected to respond to Shanahan's remarks.

The Sino-US rivalry has placed many Asian countries in a bind as they have deep military ties with Washington but enjoy strong trade relations with Beijing.

"The uncertain relationship between the US and China will remain as an explicit factor in shaping the stability of the Asia-Pacific region particularly that of Southeast Asian countries," Malaysian Defence Minister Mat Sabu told the conference Saturday.

"If anything happens in the South China Sea, the world also will suffer. We have to increase our defence diplomacy. We love America, we also love China."

Agence France-Presse