John Isner and Reilly Opelka played out a marathon 46-point tiebreak, the longest in ATP Tour history, at the Dallas Open on Saturday as Opelka edged out his fellow American 7-6(7) 7-6(22) to reach the final.

Isner was involved in the longest match of all-time against Frenchman Nicolas Mahut in the first round of Wimbledon in 2010. The pair battled it for 11 hours five minutes across three days before Isner took the fifth set 70-68.

"The crowd was definitely behind me," said the 36-year-old Isner. "It's kind of extra disappointing to not be able to get over the line in my backyard... (Opelka) is serving just massive. I don't think anyone can break him out there."

The big-serving duo fired down 60 aces between them and did not face a single breakpoint in a match lasting two hours three minutes.

"I lost track," said Opelka, the world number 23, who clinched victory on his eighth match point. "At one point it was 21-all... that's something I've never seen before, but if it was going to happen, it certainly would have been in this match."

Second seed Opelka will take on Jenson Brooksby in the final of the ATP 250 event on Sunday after his compatriot saved four match points to overcome Marcos Giron 6-4 6-7(4) 7-6(5) in the other semi-final.