Joe Biden on Wednesday declared triumphantly that "The United States is back!", as he kicked off his first overseas tour as president, hoping to leave behind the rancour and isolation of the Trump era.

Biden ran through a packed itinerary that takes in a G7 leaders' meeting and a NATO summit before ending with a face-to-face with Russian President Vladimir Putin in Geneva.

With Putin, he told US service personnel at Royal Air Force base Mildenhall in eastern England, he will "let him know what I want him to know".