Saint Petersburg - Top seed Dominic Thiem beat Spaniard Roberto Bautista Agut in straight sets on Saturday to set up a St Petersburg Open final against Slovakia's Martin Klizan.

Thiem, ranked eighth in the world, claimed his first win over the 30-year-old Bautista Agut, 6-4, 6-3, in their fourth meeting.

Klizan, the 2012 champion, battled back from a set down to beat Swiss star Stan Wawrinka 4-6, 6-3, 7-5.

"I was serving really good today," Thiem said. "I had some tough service games when I was 30-0 down and I always saved myself with some very good serves.

"Of course I want to win this title. If I win it will be my first ever indoor title and it means a lot to me."

Thiem broke Bautista Agut in the 10th game to take the opening set, and the 25-year-old Austrian made inroads on his opponent's serve at 3-2 in the second set before wrapping up victory.

Earlier on Saturday, triple Grand Slam champion Wawrinka, a wildcard entry, broke Klizan in the first game of the match to forge ahead at the Sibur Arena.

On his own serve, Wawrinka did not even allow Klizan to reach deuce until the sixth game of the second set.

But the Swiss seemed to suddenly lose his nerve, making a catalogue of unforced errors to allow the Slovak to break to love. Klizan went on to take the set.

In the deciding set, Klizan broke in the third game. Wawrinka quickly broke back but 29-year-old Slovak produced the deciding break in the 11th game to win the set and the match.

"It was a very tough match," Klizan said. "Stan is one of the best players in the world and I'm really proud of myself after I could beat him finally.

"I'm going to do my best to win the title here. It's always a pleasure to play in the final."