Top seed John Isner booked his spot in his eighth Atlanta Open final, defeating Aussie Matthew Ebden 6-4, 6-7 (6/8), 6-1 in the semi-finals.
The hard-serving Isner avenged his only loss to Ebden in five career ATP Tour meetings when the Aussie beat him earlier this year at the Australian Open.
"It was tough," Isner said. "Just like Friday, I was able to get out early in the third set and that definitely took some pressure off.
"I'm very happy to be back in the final here."
In the final the 33-year-old Isner will face fellow American Ryan Harrison, who beat Britain's Cameron Norrie 2-6, 6-3, 6-2.
Isner has won eight of his nine semi-finals in Atlanta, and will look to improve his record of 13-12 in finals.
Isner appeared to be cruising to victory, leading by a set and up by a break, when the wheels almost fell off.
The fourth-seeded Ebden broke back in the second and then saved one match point in the ensuing tie-break when Isner flubbed a backhand return.
Isner rebounded by breaking Ebden twice in the deciding set. He smashed 26 aces, using the confidence from his victory at the Miami Open and run to the Wimbledon semi-finals to win in exactly two hours.
Danilovic wins
Moscow: Olga Danilovic clinched her first WTA title on Sunday with a 7-5, 6-7 (1/7), 6-4 win over Russia's Anastasia Potapova in a battle of 17-year-olds in the Moscow final.
Serbian Danilovic, the world number 187, is the first lucky loser to win a WTA tournament having initially lost in the final round of qualifying.
At 17 years and seven months, she is the youngest champion since Ana Konjuh of Croatia won the Nottingham event in 2015, and becomes the first player born in the 2000s to win a WTA trophy.
It was the first final featuring two players under the age of 18 since Nicole Vaidisova, 16, beat Tatiana Golovin, 17, to win the Japan Open in 2005.