HANOI (AP): US Secretary of Defence Lloyd Austin is seeking to bolster ties with Vietnam, one of the Southeast Asian nations embroiled in a territorial rift with China, during a two-day visit starting Wednesday.

In a speech in Singapore, his first stop in the region he is visiting for the first time as member of President Joe Biden's Cabinet, Austin said on Tuesday he was committed to pursuing a constructive, stable relationship with China, including stronger crisis communications with the People's Liberation Army.

But he repeated that Beijing's claim to virtually the entire South China Sea "has no basis in international law" and "treads on the sovereignty of states in the region."

He said the US continues to support the region's coastal states in upholding their rights under international law, and remains committed to the defense treaty obligations the US has with Japan and the Philippines.

"Unfortunately, Beijing's unwillingness to resolve disputes peacefully and respect the rule of law isn't just occurring on the water," Austin said. We have also seen aggression against India ... destabilizing military activity and other forms of coercion against the people of Taiwan ... and genocide and crimes against humanity against Uyghur Muslims in Xinjiang."

Austin is scheduled to meet his Vietnamese counterpart, Phan Van Giang, on Thursday morning. He leaves for the Philippines on Friday.

Vietnam and the Philippines are among China's fiercest opponents in the territorial disputes in the South China Sea, where Beijing has ignored its neighbours' protests and has constructed several islands equipped with airstrips and military installations. Vietnam has previously accused China of obstructing its gas exploration activities off its southern shores.

Austin's visit comes as Vietnam is in the grip of a coronavirus surge, with Hanoi and half of the country in lockdown.