US Defence Secretary Pete Hegseth has urged Asian allies to ramp up military spending to counter China's growing power and prevent its dominance in the region, claiming there is "rightful alarm" over China's rapid military buildup.

Hegseth, speaking at the Shangri-La Dialogue in Singapore on Saturday, Asia's premier forum for defence leaders, militaries and diplomats, said stronger, more self-reliant allies are key to deterrence.

"There is rightful alarm regarding China's historic military buildup and the expansion of its military activities in the region and beyond, " he said.

"A Pacific dominated by any hegemon would unravel the regional balance of power," Hegseth said. "No state, including China, can impose hegemony and hold the security of our nation and our allies in question."

The US expects its Asian allies and partners to increase defence spending to 3.5 percent of GDP as it pledged a $1.5 trillion investment in its military, the Pentagon chief said.

'No freeloading'

Hegseth stressed allies want stability, not escalation.

"What they want, and what the United States delivers, is strength that is disciplined, resolve that is steady, and leadership that is confident enough to speak and walk softly while carrying a big stick."

Hegseth added ties with Beijing are "better than they have been in many years," citing increased military-to-military contacts.

"We are meeting more frequently with our Chinese counterparts by maintaining open lines of military to military communication."

Since returning to office, US President Donald Trump has demanded that allies boost defence spending and has pointedly said European and NATO partners should reduce reliance on Washington.

"The era of the United States subsidising the defence of wealthy nations is over," Hegseth said. "We need partners, not protectorates," he added.

"We don't have a strong alliance unless everyone has skin in the game. No freeloading."