The apparent misstatements are the latest in a series of gaffes by the 76-year-old Democrat who is seeking his party's nomination to challenge President Donald Trump in 2020.

They also raise questions about Biden's advancing age and fitness, and whether he has the endurance needed to stay on top in what will be a grueling, 18-month campaign.

Speaking last Friday at a New Hampshire campaign event, Biden recalled how a four-star general asked him to travel to Kunar province to bestow a medal on a US Navy captain who had rappelled down a ravine under fire to retrieve the body of a fellow soldier.

Biden said he had dismissed concerns that the trip into "godforsaken country" was too risky.

"We can lose a vice president," he told the rapt audience. "We can't lose many more of these kids. Not a joke."

When he went to pin the medal on the soldier, "he said 'Sir I don't want the damn thing. Do not pin it on me, sir!'" Biden recalled, his voice rising. "Please, sir, do not do that. He died. He died."

The former vice president, who has travelled more than 20 times to Afghanistan as president Barack Obama's deputy and more than three decades in the US Senate, described the retelling as "the God's truth, my word as a Biden."

But the facts were wrong, according to the Post, which interviewed more than a dozen US troops, their commanders and Biden campaign officials. The newspaper concluded that Biden had conflated elements of three actual events into a single story.

According to the Post, the soldier, Kyle White, was a 20-year-old US Army specialist, and the award he received for valor, the Medal of Honor, was placed around his neck by Obama.

Biden traveled to Kunar province in 2008 as a senator, not as vice president.

In 2011, Biden did pin a Bronze Star on a soldier in Afghanistan, US Army Staff Sergeant Chad Workman, who had run into a vehicle to try to save a dying comrade.

In a three-minute span in New Hampshire, Biden got the time period, the act of bravery, the type of medal, the military branch and the rank of the recipient wrong, as well as his own role in the ceremony, the Post reported.

Biden himself pushed back on suggestions he bungled facts from multiple events.

"I don't understand what they're talking about, but the central point is it was absolutely accurate what I said," South Carolina's Post and Courier newspaper quoted Biden on Thursday as saying.