Top seed Roger Federer has survived a stern test from world No.63 Diego Schwartzman of Argentina to advance into the final of the Istanbul Open after a tense three-set encounter.

Federer, 33, looking to win his 85th career title ahead of the French Open, looked rattled all Saturday afternoon as he failed to find rhythm on his first serve and even received a rare code violation.

Losing the first set, he eventually prevailed 2-6 6-2 7-5 after almost two hours on court.

Showing no sign of nerves in front of his illustrious opponent, the 22-year-old Schwartzman came out fighting in the first set with his double-handed backhand particularly potent.

In a sign of the pressure, the usually mild-mannered Federer received a code violation warning from umpire Mohamed Lahyani for whacking the ball away in anger when he failed to convert a break point.

After breaking the frail Federer serve twice, Schwartzman took the first set with ease when the out-of-sorts Swiss world No.2 tamely netted a return into the net.

Schwartzman came out in the second set with similar aggression but after squandering one break point in the fourth game Federer took his second chance in what proved a turning point.

Turning on the power and with Schwartzman starting to make unforced errors after his glorious first set, Federer raced ahead and took the second set with a service break to love.

With a tough struggle shaping up in the third set, Federer saved two break points in the fifth game, yelling “come on!” and saving his serve with an ace.

But Schwartzman stepped up a gear once more, matching Federer shot for shot in a thrilling finale.

Serving to stay in the match at 4-5, Schwartzman saved one match point with another stunning backhand winner.

But Federer then made no mistake as he attacked the Schwartzman serve at 5-6, taking his first break point chance to close out the game.

In Sunday’s final, Federer will face the winner of the other semi final between second seed Grigor Dimitrov of Bulgaria and Pablo Cuevas of Uruguay.