Hegseth, who is taking part in the two-day ASEAN defence ministers and related meetings in Cebu, the Philippines, said the US would back that commitment with practical co-operation, including stronger maritime domain awareness, greater interoperability and cooperation among navies.
"These are not symbolic things. They are concrete demonstrations of what serious partners do," he said on Wednesday.
"Serious partners train together, learn together, plan together and build confidence and competence necessary to prevent conflict."
Hegseth is visiting the region as governments in Southeast Asia and the wider Asian region weigh Washington's ability to stay focused on the Asia Pacific as the Iran war strains US military resources and creates political pressure at home.
The defence secretary described the US approach as "strong, quiet and clear", saying it would be "strong enough to deter coercion and aggression", quiet enough to avoid "needless escalation or public theatrics", and clear enough that friends and potential adversaries understood Washington's position.
"We will defend our interests and the interests of our allies and partners. That is, by definition, peace through strength," Hegseth said.
Hegseth also proposed developing a US-ASEAN framework for defence co-operation to guide ties during what he said would be the "critically important next several years", as the two sides mark half a century of formal relations in 2027.
Southeast Asia is grappling with the effects of the Iran war, while tension between the Philippines and Beijing has added another source of friction to a forum meant to promote dialogue and practical cooperation on security.
The Iran war, which began with US and Israeli strikes on February 28, has disrupted global shipping and oil markets, exposing Southeast Asia's vulnerability to imported-fuel shocks and pushing energy security further up ASEAN's agenda.
Greg Poling, director of the Asia Maritime Transparency Initiative, which tracks developments in the South China Sea, said Hegseth would get an opportunity at the gathering to tackle aspects regarding China, the South China Sea and Washington's commitments to its treaty allies.
The topic is critical for the Philippines, a US treaty ally whose ties with Beijing have soured amid repeated confrontations in the disputed South China Sea, Chinese sanctions and, more recently, a summoning of the Chinese ambassador.
China's defence attache in the Philippines would attend the meeting, its defence ministry said on Tuesday.
Defence chief from the "Squad", an informal grouping of the United States, Japan, Australia and the Philippines, are also set to meet on Wendesday.
Hegseth will also join an expanded defence ministers' meeting on October 29, bringing together ASEAN's 11 members and eight partners, including Australia, China, India, Japan, New Zealand, South Korea and Russia.
