Jo-Wilfried Tsonga kept the pressure on his rivals in the battle for ATP World Tour Finals spots by beating Vienna Open top seed Alexander Zverev to reach the semifinals.

Tsonga boosted his chances of claiming one of the two remaining places in the season-ending tournament in London by winning the European Open last weekend and moved a step closer to back-to-back titles with a 7-6 (8-6), 6-2 defeat of Zverev on Friday.

The energetic Frenchman is the only seed still in the tournament in the Austrian capital and will be only 95 points adrift of Pablo Carreno Busta, who occupies the last ATP Finals qualifying spot, if he claims back-to-back titles this weekend. 

Eighth seed Tsonga lost the first three games of the match but got into his stride to win the next three and edged a tie-break which swung back and forth.

World No. 5 Zverev broke again in the first game of the second set, but Tsonga was a man on a mission and claimed a further three breaks to move into the last four.

Philipp Kohlschreiber will be the next man who will attempt to halt Tsonga's charge after the German beat Diego Schwartzman 7-5, 7-6 (8-6).

Lucas Pouille overcame Richard Gasquet 7-6 (7-5), 6-1 in an all-French quarterfinal and will take on Kyle Edmund, who got past Jan-Lennard Struff 6-2 7-5.