"When we look across the region today, there is rightful alarm regarding China's historic military build-up and the expansion of its military activities in the region and beyond," Hegseth told Asia's premier defence summit in Singapore.

He added that Washington did not seek "needless confrontation in the region".

Hegseth was speaking at the Shangri-La Dialogue, which brings together top defence officials and experts from around 45 countries.

It has historically provided a setting for both open debate and behind-closed-doors diplomacy.

In his headline speech, Hegseth said Washington sought "a genuinely stable equilibrium (in Asia) that works for Americans as well as our allies".

That means "a favourable but durable balance of power in which no state, including China, can impose its hegemony and hold the security or prosperity of our nation and our allies in question", he added.

Hegseth is leading a bumper US delegation, in stark contrast to rival China, which has sent a panel of military experts and scholars instead of defence minister Dong Jun for the second year running.