US Defense Secretary Lloyd Austin met his Vietnamese counterpart in Hanoi on Thursday to advance cooperation in security, as the US and southeast Asian nations watch China's activities in the South China Sea.

Austin and Vietnamese Defense Minister Phan Van Giang discussed working together to resolve the legacies of the Vietnam War, which ended in 1975. 

According to the Vietnamese Defense Ministry, the two addressed issues such as continuing searches for American MIAs, removal of landmines and the decontamination of Agent Orange, the powerful defoliant dioxin used by US soldiers during the war. 

The two sides also signed a "memorandum of understanding" for Harvard and Texas Tech University to create a database that would help Vietnamese search for those who went missing during the war. 

Tensions over the South China Sea

Vietnam is one of China's staunchest opponents in the territorial rifts in the South China Sea — a region where Beijing has constructed a number of islands equipped with airstrips and military installations, despite its neighbors' protests. 

Vietnam has also accused China of obstructing its gas exploration activities off its southern shores. 

"One of our central goals is ensuring that our allies and partners have the freedom and the space to chart their own futures," Austin said ahead of the meeting in Hanoi. 

He stressed that the US did not ask Vietnam to choose between countries.

On Wednesday, a US Navy warship carried out a transit through the Taiwan Strait.

Such operations, though routine, irk China. 

Despite deepening ties between Washington and Hanoi, US President Joe Biden's administration has emphasized that there are limits to the relationship until Vietnam makes progress on human rights.  

Austin on Wednesday also discussed non-traditional security cooperation with Vietnam  in natural disaster relief and COVID-19 pandemic recovery.

Vietnam is battling a fierce COVID-19 surge with half the country, including Hanoi, in a lockdown.

The US has donated five million doses of the Moderna vaccine to Vietnam as part of the 80 million doses that Biden pledged to lower-income countries.

dvv/nm (AP, Reuters)