Obama implores Vietnam to embrace human rights

US President Barack Obama told communist Vietnam on Tuesday that basic human rights would not jeopardise its stability, in an impassioned appeal for the one-party state to abandon authoritarianism.

In a sweeping speech, which harked back to the bloody war that defined both nations and also looked to the future, Obama said that "upholding rights is not a threat to stability."

Vietnam ruthlessly cracks down on protests, jails dissidents, bans trade unions and controls local media.

But the US leader said bolstering rights "actually reinforces stability and is the foundation of progress", in a speech to a packed auditorium including Communist Party officials in Hanoi. 

The visit is Obama's first to the country -- and the third by a sitting president since the end of the Vietnam War in 1975. Direct US involvement in the conflict ended in 1973.

Obama's trip has formally reset the relationship between the two former wartime foes with a lifting of a US arms embargo and deepened trade ties. But he has been cautious to avoid hectoring his hosts on rights.

"Vietnam will do it differently to the United States," Obama said. 

"But these are basic principles that we all have to try to work on and improve," he added, referring in particular to the importance of a free media.

His speech, punctuated with humourous asides and references to Vietnamese culture and history, was greeted with warm applause in the cavernous National Convention centre. 

Earlier Obama met civil society leaders, including some of the country's long-harassed critics.

But in a country where state control remains the reflex response, authorities stopped some activists from meeting him.