Joe Biden has marked the 80th anniversary of D-Day by saying "we will not walk away" from the defence of Ukraine and allow Russia to threaten more of Europe.
The US President drew parallels between Germany’s onslaught on Europe with Russia’s invasion of Ukraine, during a speech on Omaha beach.
Ukrainian leader Voldomyr Zelensky watched on as Biden pledged his solidarity in front of assembled world leaders.
He said: "To surrender to bullies, to bow down to dictators, is simply unthinkable," the US president said during a ceremony at the US cemetery in Normandy.
"If we were to do that, it means we'd be forgetting what happened here on these hallowed beaches."
D-Day was the largest amphibious assault in history, and Mr Biden called it a "powerful illustration of how alliances, real alliances, make us stronger", adding that was "a lesson that I pray we Americans never forget".
Speaking about the US troops who stormed Normandy's beaches on June 6 1944, Mr Biden said "let us be worthy of their sacrifice".
"We must remember that the fact that they were heroes here that day does not absolve us of what we have to do today. Democracy is never guaranteed. Every generation must preserve it, defend it and fight for it. That's the test of the ages."
French President Emmanuel Macron earlier told US veterans that "you came here because the free world needed each and every one of you, and you answered the call".He awarded the Legion of Honour to several of them, and kissed them on each cheek as he pinned on their medals.
Mr Biden and first lady Jill Biden earlier met more than two dozen US veterans near Omaha Beach, where the fiercest D-Day fighting took place. Those who could stand were helped out of wheelchairs to pose for photos. Most shook hands with Mr Biden or saluted.
The president told a veteran that "you saved the world", and led the audience in singing happy birthday to another. Steven Spielberg and Tom Hanks, the Hollywood heavyweights behind films and television shows about the Second World War, were nearby.
When Army veteran Robert Gibson approached, the first lady clutched his arm to help him stand next to the president as they shook hands."Don't get old," the 100-year-old man from New Jersey joked to the 81-year-old president, who was a toddler on D-Day.
This anniversary of the invasion is a particularly sombre one because it will be among the last with living veterans - the youngest survivors are in their late 90s.Mr Biden met one veteran who is 104.
In an interview with the Associated Press a few days ago, Mr Gibson described himself as "living on borrowed time".
He was part of the second wave of troops that landed on Utah Beach. He said he expected this year would be the last anniversary ceremony he could attend, but he was pleased to be back one more time.
"I want to see the beach again," he said.
