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 will take on either No. 2 Rafael Nadal or No. 3 Roger Federer in today's final, with Isner trying to become the first American winner in the desert since Andre Agassi in 2001.

Nadal and Federer were to play in the other semifinal, although rain began falling shortly after Isner left the court.

Victoria Azarenka and Maria Sharapova will meet for the women's title Sunday.

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.

"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 advantage with his serve-and-volley game. Isner hit several serves of more than 140 mph.

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'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.

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