President Joe Biden phoned the United States team in Qatar to urge Gregg Berhalter's players to "shock 'em all" at the World Cup.
Ahead of their opening game against Wales on Monday, the team gathered to listen to Biden offer words of encouragement to a group he acknowledged were outsiders.
The United States men's team took third place at the inaugural 1930 World Cup but have never gone further than the quarter-finals since, only reaching that stage once, in 2002.
By comparison, the US women's national team are four-time World Cup winners, and will be chasing a hat-trick of consecutive titles at next year's finals in Australia and New Zealand.
Biden, who turned 80 on Sunday, told Berhalter: "Coach, put me in, I'm ready to play."
He added: "You guys, I know you're the underdog, but I'll tell you what, man, you got some of the best players in the world on your team, and you're representing this country, and I know you're gonna play your hearts out, so let's go shock 'em all.
"Keep trusting in one another, play as hard as you can, for you and your families, your team-mates, and the whole country is rooting for you."
Berhalter replied: "That's a very nice message, Mr President, the whole team is here right now and we really appreciate your support and we're ready to go."
The United States also face England and Iran in Group B, returning to the World Cup stage after missing out on the Russia 2018 finals.
Biden added: "I wish I were there to see you, I really do, go get 'em guys, just play your hearts out. I know you will, I know you will."
