Frances Tiafoe will face Taylor Fritz in the semi-final of the US Open, where there will be an American in the men's final for the first time in 18 years.

After Fritz overcame Alexander Zverev, Tiafoe faced Grigor Dimitrov in a bid to tee-up an all-American semi-final in New York.

And Tiafoe was 2-1 up in sets and 4-1 up in the fourth when Dimitrov was forced to retire due to injury.

That means there is guaranteed to be an American in the final at Flushing Meadows for the first time since Andy Roddick faced Roger Federer in 2006.

"I didn't want to end it like that, for me or the crowd. But Friday is going to be one hell of a day," said Tiafoe.

"It's the biggest match of mine and Taylor's life.

"Obviously, it's not the way I wanted to get through but being in another semi-final here is incredible."

Data Debrief: Fortunate sons

This is the first time two Americans have reached, and will face each other, in the last four of a grand slam since Andre Agassi went up against Robby Ginepri in 2005, at Flushing Meadows.

Indeed, the United States has not had a men's singles major champion since Roddick triumphed at the US Open in 2003.