Joe Biden suggested his uncle may have been eaten by cannibals in New Guinea during World War Two.
The US President visited a war memorial to honour his uncle Ambrose J Finnegan for his service.
Following the service, Biden told reporters: "He flew single-engine planes, reconnaissance flights over New Guinea. He had volunteered because someone couldn't make it.
"He got shot down in an area where there were a lot of cannibals in New Guinea at the time. They never recovered his body."
The US president suggested his uncle may have been eaten by cannibals in New Guinea during World War Two
Getty
But according to US military records, his uncle died when a plane he was in crashed in the Pacific Ocean off the northern coast of New Guinea in May 1944 following an engine failure.
There appears to be no record that his death was related to any hostile action or that cannibals played any part in recovering his remains.
Biden added: "We have a tradition in my family my grandfather started. When you visit a gravesite of a family member - it's going to sound strange to you - but you say three Hail Marys. And that's what I was doing at the site."
The Potus also compared his family's record of sacrifice to comments allegedly made by Donald Trump about fallen soldiers.
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The remarks were reportedly made in 2018 when he did not want to visit a cemetery for American war dead in France, according to his former aides.
Trump has denied these allegations.
Biden continued saying that the Republican candidate "doesn't deserve to have been the commander-in-chief for my son, my uncle."
The President has linked the death of his son, Beau who suffered with brain cancer, to his deployment in Iraq - where the military used burn pits to dispose of waste.
Joe Biden visited a war memorial to honour his uncle Ambrose J Finnegan for his service
Reuters
White House spokesman Andrew Bates told NBC News that the President was "proud of his uncle's service in uniform, who lost his life when the military aircraft he was on crashed in the Pacific after taking off near New Guinea."
He added: "The President highlighted his uncle's story as he made the case for honouring our 'sacred commitment... to equip those we send to war and take care of them and their families when they come home'
"And as he reiterated that the last thing American veterans are is 'suckers' or 'losers'."