President Barack Obama praised the humble heroism of US soldier Clinton Romesha on Monday, awarding him a Medal of Honor for his actions in one of the most desperate firefights of the Afghan war.

Army Staff Sergeant Romesha, 31, fought off fierce enemy fire despite being wounded, in a 12-hour siege of an exposed mountain outpost in 2009 in which 53 American soldiers were pinned down by 300 Taliban fighters.

Eight Americans died and 22 were wounded in fighting that Obama described "as one of the most intense battles of the entire war in Afghanistan."

"The attackers had the advantage, the high ground, the mountains above, and they were unleashing everything they had, rocket-propelled grenades, heavy machine guns, mortars, snipers taking aim," Obama said.

Despite shrapnel wounds to his hip, an arm and his neck, Romesha repeatedly charged into enemy fire -- once through a 100 meter hail of bullets, to rescue wounded Americans and the bodies of the dead.

"These men were outnumbered, outgunned and almost overrun," Obama said, at an emotional ceremony in the East Room of the White House in which he conferred America's highest individual military honor on Romesha.

"Looking back, 'one of them said, I'm surprised any of us made it out.'"

Obama said the scale of heroism shown on that day was evidenced in the list of decorations conferred in the aftermath, including 37 Army Commendation Medals, 27 Purple Hearts, 28 Bronze Stars and nine Silver Stars."

"There are many lessons ... one of them is that our troops should never, ever be put in a position where they have to defend the indefensible," he said.

"That's what these soldiers did for each other, in sacrifice driven by pure love."

The official military citation accompanying Romesha's medal, said he shot dead three Taliban fighters who had breached the perimeter of the outpost and "destroyed multiple enemy targets."

Romesha, his hands shaking with emotion as he fought to control his emotions, later told reporters that he accepted the medal on behalf of his comrades that did not make it home.

"I stand here with mixed emotions, of both joy and sadness," Romesha said outside the White House, with the blue ribbon of the medal around his neck, as he mourned his lost "battle buddies" in Afghanistan.

"I accept this tremendous honor of behalf of all soldiers who have served with me that day. This award is for the eight soldiers that did not make it and for the rest of the team that fought valiantly and magnificently."

Romesha, now retired, served two tours in Afghanistan and four in Iraq, and now lives with his family in North Dakota.