Washington DC - President Donald Trump downplayed the role of European countries in World War II on Wednesday as he formally designated May 8 as a day to celebrate victory over Nazi Germany.

"The victory was mostly accomplished because of us, like it or not," Trump said at the White House shortly after issuing a proclamation on the new "Victory Day."

"It was American tanks and ships and trucks and airplanes and service members that vanquished the enemy 80 years ago this week. Without America, the Liberation would never have happened."

Trump had announced his intention to rename May 8 earlier this week, noting that unlike much of Europe, his country had no day to mark the defeat of Nazi Germany in 1945.

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Trump said he also planned to establish a separate "Victory Day" for World War I – and claimed US credit for ending that conflagration too.

"Without us, those wars would not have been won," he said.

Trump's comments came despite the fact that many European allies suffered far more casualties and devastation than the United States in the two global conflicts.

The US suffered significant losses after joining World War II in 1941, with more than 400,000 service members killed, and played a crucial role in the D-Day landings and the defeat of Adolf Hitler.

The Soviet Union, of which Russia was the largest republic, suffered the most with more than 20 million killed.

Britain lost 384,000 soldiers and 70,000 civilians in World War II.