The United States warned China on Saturday against threatening its neighbours' sovereignty and said Washington was investing in new military technology in the next five years to keep Asia stable.
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 also being held against a backdrop of Sino-US trade tensions and high-tech rivalry.
"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 Defence 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."
Washington has been pushing back against Beijing's militarisation of the South China Sea, where China has built installations to enforce blanket sovereignty, pitting it against partial claims by Taiwan, Brunei, Malaysia, the Philippines and Vietnam.
Beijing is also regularly angered by US warships transiting through the Taiwan Strait, which it considers part of its territorial waters.
For the first time since 2011, China has sent its defence minister, General Wei Fenghe, to the Singapore gathering. Wei is scheduled to speak on Sunday during which he is expected to respond to Shanahan's remarks.
'Indo-Pacific is our priority'
Shanahan said the US was investing heavily in the Indo-Pacific region to maintain its military superiority and capability to defend its Asian allies.
"North Korea remains an extraordinary threat and requires continued vigilance," Shanahan said.
"The Indo-Pacific [region] is our priority theatre. We are where we belong. We are investing in the region," he added.
"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 US does not seek conflict, it knows that having the capability to win wars is the best deterrence."
"We want to ensure no adversary believes it can successfully achieve political objectives through military force," he said.
He said the Pentagon has requested $104 billion globally — its most ever — for research and development in the next fisal year and $125 billion in operational readiness.
On Friday, Beijing warned that the US should not underestimate China's military during a meeting between Shanahan and Wei on the sidelines of the conference.
Chinese defence ministry spokesman Wu Qian said both had "reached some consensus" on issues of common concern, adding that Wei "particularly emphasised the Taiwan issue".
China sees Taiwan as part of its territory to be reunified, despite the two sides having been ruled separately since the end of a civil war on the mainland in 1949.
"He (Defence minister Wei) pointed out that the US has recently had a series of negative words and actions on this issue", Wu said, adding that Beijing was "firmly opposed" to this.
"On the issue of safeguarding national sovereignty and territorial integrity, the US should not underestimate the determination, will and ability of the Chinese military."