Legendary US documentary maker Ken Burns's new 18-hour television history of the Vietnam war is a "visceral" experience which will make viewers feel like they had lived through it, his co-director said Sunday.

His longtime creative partner Lynn Novick said they had spent a decade talking to hundreds of veterans from both sides of the bloody conflict in which as many as 3.6 million people may have died.

She said now was the time for the monumental opus, which will screen on US public TV every weekday night for a fortnight in September.

"This is a time of reckoning. We are facing this very painful chapter and try to unpack it," Novick said.

"The generation who passed through the war are only ready now to have this kind of conversation," she told AFP after showing a preview of the series at the top TV gathering, MIPTV, in Cannes on the French Riviera.

"This was one of the most important events in the world since World War II and yet it's among the least understood. Most Americans do not understand it or why it happened and we are very upset about it to this day," she added.

- 'Decade of agony' -

"The Vietnam War was a decade of agony that took the lives of more than 58,000 Americans," said Burns, who is best known for his acclaimed history series "The West" and "The Civil War".

"Not since the Civil War have we as a country been so torn apart" by a conflict, he said.

"There wasn't an American alive then who wasn't affected -- from those who fought and sacrificed in the war to the families of services members and POWs, to those who protested."

Using often previously unseen archive footage and photographs from Vietnam, Russia and France, Novick said they have attempted to reconstruct how the conflict began with interviews from players and survivors on all sides.

But most of it deals with the experience of those on the ground, the soldiers and civilians who did the fighting and the dying.

"It is an immersive visceral experience that makes you feel that you have gone through the war yourself," Novick said.has filmed

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"It opens people up in a remarkable way. We have something very serious we cannot wait to unleash on the world."

- Pit of death -

In one sequence a North Vietnamese survivor talks about how "the war seemed like an open pit" that was swallowing his people.

A Viet Cong veteran was struck by the tenderness with which the Americans treated their wounded comrades, and said it was only then he realised that "the Americans have humanity just like us".

Both Burns and Novick said the series was "the most challenging project we have ever undertaken because we wanted to understand this not just from the many American points of view, but also from the perspective of the Vietnamese."

"The story of this war has never been told this way before and may never be able to be told this way again given the age of the witnesses," Novick added.

Estimates vary on the numbers of people who died during the conflict, from more than 1.4 million to nearly 3.6 million.

Novick said the war still has strong resonance.

Like many wealthier Americans, including Donald Trump, the sons of top Vietnamese communist officials were able to avoid the draft by studying at university, or were sent off to the Soviet Union.

"Many of the seeds of what we see as distressing in the world today can be found back in the time of the Vietnam War. It is more relevant than ever," Novick said.