Hegseth is expected to meet defense ministers from India, Indonesia, the Philippines and Thailand, among others, said an official speaking on condition of anonymity, who warned the schedule could change.

It was not clear if the Pentagon chief would meet any Chinese officials while in the Malaysian capital for the two-day meeting.

In his meeting with Indian defense minister Rajnath Singh, Hegseth was expected to discuss a review of India's plans to buy US military hardware, as well as a new India-US defense cooperation framework.

Delegations from Australia, China, New Zealand, South Korea and Russia are also attending the meeting of defense ministers of the Association of Southeast Asian Nations.

Chinese grey-zone tactics

Hegseth met Malaysia's defense minister on Thursday and both leaders committed to maritime security in the disputed South China Sea.

Beijing has deployed a coast guard armada in the busy waterway that has clashed repeatedly with Philippine vessels and been accused of disrupting the energy activities of Malaysia and Vietnam.

"Grey-zone tactics, such as hydrographic research conducted under the protection of foreign coast guard vessels, threaten sovereignty and are a clear provocation and threat," Malaysian Defense Minister Mohamed Khaled Nordin said in a joint statement.

China claims almost the entire South China Sea on its maps, overlapping with the exclusive economic zones of Brunei, Malaysia, the Philippines and Vietnam.

Unresolved disputes have festered for years over the sovereignty of multiple islands and features.

Beijing says its coastguard has operated professionally in defending Chinese territory from incursions.

The US has sought to shore up its presence in Southeast Asia and counter the growing influence of China.

On Sunday, President Donald Trump told ASEAN leaders the US was "with you 100% and we intend to be a strong partner for many generations".

Washington has a defense pact with the Philippines that involves dozens of annual military drills and use of some of its bases, in addition to similar exercises with Thailand and Indonesia and exchanges with Malaysia.

Order to resume nuclear testing

Shortly before meeting Chinese counterpart Xi Jinping on Thursday, Trump said he had ordered the US military to resume nuclear weapons testing amid a rapid expansion of China's nuclear stockpile.

His administration's efforts to persuade its allies to spend more on defense have caused friction, but Japan's Prime Minister Sanae Takaichi told Trump this week that she was determined to boost defense capabilities.

On Wednesday, Hegseth urged Japan to hasten plans to boost defense spending to 2 percent of GDP, saying the alliance between Washington and Tokyo was "critical to deterring Chinese military aggression".