Vietnam president To Lam warned in the keynote address at the 23rd Shangri-La Dialogue that three crises are converging in the Asia-Pacific region.
To Lam told defence ministers, military chiefs and diplomats at the Singapore meeting that these challenges reinforce each other.
He described the Asia-Pacific as a growth centre yet one facing maritime risks, supply chain fragmentation, climate change and technological transition pressures.
US Defence Secretary Pete Hegseth is scheduled to deliver his address on Saturday morning, which is expected to offer the first indication of American policy direction in the Indo-Pacific following the Trump-Xi summit.