Eighth-seeded John Isner has blasted 29 aces to reach the final of the ATP and WTA Washington Open with a 6-7 (7-9) 6-3 6-4 victory over Dmitry Tursunov.

America’s Isner fired four aces to hold serve in the final game and 10 overall in the last set as he earned the chance to play for his eighth career ATP title, a third crown of the year and second in as many weeks.

The 28-year-old American will play Sunday’s final against the winner of the later semi-final between German third seed Tommy Haas and top seed Juan Martin Del Potro of Argentina.

Isner is 3-3 against Haas but 0-3 against Del Potro.

Isner, who won last week in Atlanta and last April in Houston, advanced to his 15th career final and his second at this hardcourt event, having finished second to Andy Roddick in 2007.

Isner, ranked 20th, tops the season ATP rankings in aces with 587 in 37 matches and has a tournament-best 78 this week.

He also leads the ATP in break points save percentage but did not face a break point in the match.

Tursunov, ranked 61st, was seeking his eighth ATP title and first final since winning in 2011 at s-Hertogenbosch.

Seventh-ranked Del Potro, the 2009 US Open winner and the Washington champion in 2008 and 2009, is playing his first event since losing an epic Wimbledon semi-final to top-ranked Novak Djokovic.

Del Potro, seeking his 15h career ATP crown and second of the year after Rotterdam in February, seeks his 13th win in a row at Washington. His most recent final was at Indian Wells, where he lost to Rafael Nadal.

In later women’s semi-finals, defending champion Magdalena Rybarikova, the seventh seed from Slovakia, was to face Russian third seed Ekaterina Makarova and French fourth seed Alize Cornet was to play Germany’s Andrea Petkovic.