President Barack Obama on Monday said the treatment of returning Vietnam veterans had been a national shame and disgrace and pledged no repeat for US military personnel serving in today's war zones.

In a speech marking Memorial Day at the Vietnam War Memorial in Washington, where the names of 58,000 soldiers, airmen, sailors and Marines are engraved, Obama said the fallen and those who survived should be proudly honored.

"One of the most painful chapters in our history was Vietnam -- most particularly, how we treated our troops who served there," he told a crowd that included veterans of the conflict that spiraled out of control in the 1960s.

"You were often blamed for a war you didn't start, when you should have been commended for serving your country with valor. You were sometimes blamed for misdeeds of a few, when the honorable service of the many should have been praised.

"You came home and sometimes were denigrated, when you should have been celebrated. It was a national shame, a disgrace that should have never happened. And that's why here today we resolve that it will not happen again."

Memorial Day, the annual commemoration of fallen and missing warriors, is a national holiday and Obama spoke as tens of thousands of Americans and tourists paid tribute at the black stone memorial wall over the weekend.

"We can step towards its granite wall and reach out, touch a name," said Obama, noting that his year marks the 50th anniversary of the conflict's escalation when major US combat operations were stepped up.

"We honor each of those names etched in stone -- 58,282 American patriots. We salute all who served with them. And we stand with the families who love them still."

Obama said the US Department of Veterans Affairs aimed to ensure that those who survive conflict return home and gain the support needed to lead successful civilian lives, and praised Vietnam veterans for leading that effort.

The US is "helping hundreds of thousands of today's veterans go to college and pursue their dreams" through the GI Bill, the president said.

"Because of you, across America, communities have welcomed home our forces from Iraq. And when our troops return from Afghanistan, America will give this entire 9/11 generation the welcome home they deserve," Obama added.