WASHINGTON (AFP) - US President Barack Obama on Thursday feted three Americans who helped thwart a train attack in France, welcoming them to the White House and hailing their courage.

"They represent the very best of America," Obama said in saluting Spencer Stone, Anthony Sadler and Alek Skarlatos in the Oval Office.

"We want to say thank you to them not only for saving so many lives but also for making America look so good."

On Aug 21, the trio helped overpower a gunman armed with a pistol, an assault rifle and 270 rounds of ammunition on a Paris-bound train.

"Because of their courage, it's fair to say that a lot of people were saved," said Obama.

Their actions also made them instant celebrities.

The three have already received a parade in their home state of California and been awarded France's highest decoration, the Legion of Honour, by President Francois Hollande.

Stone, 23, a US Airman first class who is being promoted to staff sergeant next month, Army National Guard Specialist Skarlatos, 22, and Sadler, a 23-year-old civilian, were on holiday in Europe at the time of the attack.

Later on Thursday, the Pentagon will host a ceremony to award Stone the Airman's Medal, which is given to Air Force members who distinguish themselves by heroic actions.

He will also get a Purple Heart, which is normally given to troops who are wounded in combat.

Stone suffered deep slash wounds in the attack.

Skarlatos will receive the Soldier's Medal.

Sadler will get the Secretary of Defence Medal for Valour, the Defence Department's highest civilian award for valour.