France, June 4 -- Second seed Coco Gauff saw off her fellow American Madison Keys in three sets on Wednesday to reach the semi-finals at the French Open.

Gauff, 21, claimed a see-saw encounter 6-7, 6-4, 6-1 in two hours and 11 minutes.

After coming from a break down in the opener to level at 4-4, Gauff undermined her chances in the tiebreak at six games apiece with two double faults.

Staving off a set point to reach six points-all, Gauff threw in another double fault - her seventh of the set - to furnish Keys with a second set point and the 30-year-old claimed the advantage when a Gauff service return landed in the tramlines.

Gauff regrouped and, assisted by a string of errors off Key's normally reliable forehand, sped into a 4-1 lead...