INDIAN WELLS, Calif. -- John Isner fired 20 aces, including one at 135 mph on his fourth match point, to beat top-ranked Novak Djokovic 7-6 (7), 3-6, 7-6 (5) Saturday in the BNP Paribas Open semifinals.
Isner is trying to become the first American winner in the desert since Andre Agassi in 2001.
Isner's victory guaranteed he will break into the top 10 for the first time in next week's ATP Tour rankings at No. 10. A victory in the final would move the American to No. 8, passing countryman Mardy Fish who is currently in that spot.
Isner is the first American to beat a world No. 1 since James Blake defeated Federer in the 2008 Beijing Olympics.
Isner needed nearly three hours to reach his first ATP Masters 1000 series final after 25 tries. He didn't get past the round of 16 in his first 23 events until making his first semifinal in Paris last fall and now the final in the desert.
He threw his arms up and soaked in the applause from the crowd that was squarely behind him throughout the match.
"It's something that you don't experience every day," Isner said. "I was just trying to take it all in."
The 6-foot-9 American towered 7 inches over Djokovic, giving Isner an easy advantage with his serve-and-volley game. He played a few loose points in the 12th game of the final set, sending a forehand past the baseline on his first match point, and Djokovic held to force the second tiebreaker.
Isner aced Djokovic with a 143-mph serve to lead 3-2, then hit a forehand winner down the line to go up 4-2.
"I told myself I was going to run around the backhand and hit a forehand, and I was just hoping that he wasn't going to hit the serve up the T. He had been doing that quite a bit, especially on the ad side," Isner said. "I wanted to put a good hit on the ball because if you don't, he just gets you moving. That's why he's the best in the world."
Isner's 144-mph serve forced Djokovic into a netted return that set up Isner's second match point.
Even Djokovic caught himself looking at the scoreboard to see how fast Isner's serves were.
"Sometimes just to admire, because I will never get there," he said, laughing.
Isner connected on 74 percent of his first serves, although Djokovic actually won 11 more points than he did in the match. The Serb had little success lobbing to keep Isner off the net as the big guy put away smashes with confidence.
"It's a lot of pressure knowing that somebody serves that well. You need to win your service points, especially when you get to the tiebreak," Djokovic said. "But this time I was unlucky. He didn't wait for it, he went for it."
Djokovic served up a rare ace of his own and Isner committed an unforced error before closing it out with his 20th ace.
Isner's height and power had him tabbed as a future American star since he turned pro in 2007, but success has come in fits and starts. He reached his current -- and best -- career ranking of 11th just last month, when he notched his previous biggest win over Federer in a Davis Cup match on the Swiss star's home turf.
"I knew going into this year that I had the tools and I had the game to be able to at least compete with these guys. I take the court no matter who I'm playing expecting to win and believing to win," Isner said.
"There's really no reason to take the court if I believe otherwise. So the win against Roger was very big for my confidence, and obviously this one will be very big for my confidence."
There was a win over Andy Roddick at the 2009 U.S. Open, but casual fans may know Isner best for a marathon win over Nicolas Mahut at Wimbledon in 2010. They played the longest ever pro match, stretching 11 hours and 5 minutes over three days.
"I've just kept on surprising myself after each year. When I reached the top 50 in the world, that's actually when I actually did believe I could crack the top 10," he said. "I've always been a late bloomer."
Djokovic, the defending champion, fell to 14-2 this season, having lost to Andy Murray in Dubai earlier this month.
Information from The Associated Press was used in this report.