DOHA - Veronika Kudermetova upset the Doha Open seedings to beat American teenager Coco Gauff 6-2, 3-6, 6-1 on Thursday and set up a semi-final with world number one Iga Swiatek.

Russian 25-year-old Kudermetova, ranked eighth, needed just over two hours to complete victory over the world number four.

If she is to reach a first WTA final since Istanbul last April, Kudermetova will have to get past a refreshed Swiatek.

The reigning French and US Open champion reached the last-four when last weekend's Abu Dhabi title winner Belinda Bencic withdrew from their quarter-final.

Kudermetova, who will be playing in her second semi-final of the year, has not won a set from Swiatek in two previous encounters.

Polish star Swiatek hardly broke sweat in her opening match at the tournament, dropping just one game and needing only 53 minutes to defeat Danielle Collins on Wednesday.

Last season, Swiatek kicked off a 37-match win streak in Doha, where she captured her first WTA 1000-level hard-court title.