US second seed John Isner outlasted Spanish third seed Feliciano Lopez 6-7 (5/7), 7-6 (7/4), 6-3 on Saturday to reach the final of the $442,500 ATP US Men's Clay Court Championship.
As a result, the power-serving American ensured he will rise from 10th to ninth in the ATP rankings on Monday, passing Mardy Fish to become the top-rated US player in the world.
"That has been one of my goals for a long, long time," Isner said. "I'm so happy to accomplish it."
Isner, who sparked a US semi-final Davis Cup triumph on French clay to book a semi-final date with Spain in September, will seek his fourth career title in Sunday's final against Argentina's fourth-seeded Juan Monaco, who beat US qualifier Michael Russell 5-7, 6-1, 6-4 in the other semi-final.
"It's going to be difficult for me," Monaco said. "I will have to be ready with my returns."
Isner has held serve in 44 consecutive games at the only ATP clay-court event in his homeland, although he was pressed for the first two sets by the Spaniard.
"I knew going into this match it was going to be tough," Isner said. "I always find myself playing my best when my back is against the wall and tonight was no different."
Lopez broke a 4-4 deadlock in the first tie-breaker with back-to-back points before Isner saved one off the Spaniard's serve with a drop volley winner, only to net a forehand volley to drop the opening set.
Isner took advantage of his first set point in the second tie-breaker when Lopez sent a backhand wide.
In the third set, Isner smacked a backhand down the line winner to break Lopez for a 4-2 lead and held serve from there for the triumph.
Isner, a runner-up last month at Indian Wells, seeks his first clay-court ATP crown against Monaco.
"It's most likely his best surface," Isner said. "I'm going to have to play well. He's having a great year."
Monaco won his fourth career ATP title, and first since 2007, in February at Vina del Mar and reached the semi-finals last month at Miami, losing to the eventual winner, world number one Novak Djokovic.
Monaco, ranked 16th in the world, served to reach a first-set tie-breaker but hometown hero Russell broke him in five points, claiming the set when the South American netted a forehand volley.
Monaco dominated the second set and battled in the third. Trying to level the final set in the 10th game, Russell sent a backhand beyond the baseline to hand Monaco a match point, then netted a backhand to send Monaco to his 13th ATP final.
"It was a tough match," Monaco said. "It was a great win and I'm happy to be in the final."
Russell, who earlier ousted top seed Fish, was in his first career ATP semi-final in 117 tour events.
"I'm finally playing well again and I hope to use this week going forward," Russell said.