Australia has warned that China's "nuclear ambitions" and Chinese military build-up have created "daunting" and "grim" challenges across the Asia-Pacific region, media reports said Sunday.

"Beijing is credibly preparing to potentially use military force to alter the balance of power in the Indo Pacific," US Defence Secretary Pete Hegseth has warned, at a regional forum.

U.S. Defense Secretary Pete Hegseth has reassured allies in the Indo-Pacific that they will not be left alone to face increasing military and economic pressure from China.