2 Avenue Gordon Bennett, 75016 Paris, France, 3 June 2017 | AAP

Samantha Stosur believes she is peaking beautifully for another second-week tilt at French Open glory.

The Australian No.1 stormed into the fourth round for the sixth time in Paris with a 6-2 6-2 dispatch of American qualifier Bethanie Mattek-Sands.

Stosur blew Mattek-Sands off the court in barely an hour to set up a last-16 meeting on Sunday with Latvian Jelena Ostapenko.

A quarterfinal against former champion Svetlana Kuznetsova or Caroline Wozniacki looks imminent as Stosur showcased her title credentials with four aces, seven service breaks and some of the fastest deliveries of the championships.

Yet to drop a set all tournament, the victory in Stosur’s milestone 50th match at Roland Garros was her eighth in a row on European clay and thrust the 33-year-old firmly in the frame for French Open glory.

“I’m really pleased that I’ve been able to continue this form and get another straight-sets win,” Stosur said.

“I feel like I probably played a bit better again today and, yeah, I’m just really, really happy.

“Bethanie can be a really dangerous player. She obviously likes to play really aggressive and coming to net, kind of play big, and do all these things, and if you’re not on and doing the right things against her, then she could make life very difficult.

“But I felt like every time she maybe had a bit of an opportunity or something like that, I was able to play a bit better and, yeah, kind of squash that and then get myself ahead again.

“So just really pleased that I was able to play as well as I did.”

Mattek-Sands entered Court 3 with her left thigh heavily strapped and proceeded to make a horrible start.

The six-time grand slam doubles champion was flabbergasted when foot-faulted on the second point of the match.

“No way,” Mattek-Sands repeatedly protested to the chair umpire. “I never foot fault.”

Rattled, she dropped her opening two service games as Stosur steamed to a 3-0 lead for the loss of only three points.

Mattek-Sands finally got on the board in the fourth game but Stosur broke straight back before clinching the first set in 31 minutes.

The pair traded early breaks in the second set as Australia’s former finalist dropped serve from 40-15 up in the fourth game.

But as hovering storm clouds threatened to stall Stosur’s progression, the 23rd seed wrestled back control with some piercing backhand return passes and her trademark forehand power.

Clapping thunder almost forced the pair off court with Stosur five points from victory.

But after consulting officials, the umpire allowed the match to continue, with Stosur eventually wrapping up the win in one hour and 10 minutes.