John Isner will go up against Kevin Anderson in a battle of two big servers in the final of the BB&T Atlanta Open.
American Isner smashed down 21 aces before eventually coming out on top in a final-set tie-break to record a 6-4 4-6 7-6 (7/5) victory over Lleyton Hewitt.
The Australian veteran, who had won four of their previous five matches and also hit 12 aces himself, had three break points in the seventh game and another in the ninth during a tense third set.
However, he was unable to take any of the opportunities that came his way and despite battling back from a 3-0 deficit in the breaker, Isner hit a service winner to take the victory after two hours and 23 minutes.
"I thought I played very well," Isner said. "It's a case where I'm getting more comfortable, now that it's my third match out there.
"I was able to go for my shots more in this match than I was in my previous matches."
Next up is fellow beanpole Anderson, the South African having seen off Ryan Harrison 6-3 7-6 (7/3).
American Harrison dropped his serve only once in the contest but could not take any of the five break points he created for himself, as the 6ft 8in Anderson set up a showdown between the two top seeds.
Isner holds a 5-3 lead in their previous meetings, while he will also be contesting his third final in Atlanta in four years, having been beaten by compatriot Mardy Fish in both 2010 and 2011.
Meanwhile, British doubles duo Jonny Marray and Colin Fleming reached their second final of the season together as they saw off Australians Hewitt and Chris Guccione.
The Davis Cup pairing won 6-4 7-6 (8/6) and will now face France's Edouard Roger-Vasselin and Holland's Igor Sijsling, the fourth-seeded pairing having themselves fended off Israel's Jonathan Erlich and Andy Ram 3-6 6-1 10-7.