PARIS - US Open champion Sloane Stephens said Tuesday that her relationship with good friend Madison Keys will stay "normal" ahead of their French Open semi-final clash at Roland Garros -- a repeat of last year's Flushing Meadows final.

The 10th seed produced a clinical performance to down Russian Daria Kasatkina, the conqueror of world number two Caroline Wozniacki, 6-3, 6-1 on Court Philippe Chatrier in the last eight. Earlier in the day Keys, the 13th seed, reached the semi-finals for the first time by seeing off Kazakhstan's Yulia Putintseva 7-6 (7/5), 6-4.

Stephens cruised to a 6-3, 6-0 victory over Keys last September to win her first Grand Slam title in New York. "When we get on the court, it's time to compete. But before that, we are not going to be weird and awkward and make it, like, weird for each other," said Stephens, who was close to going out in the third round to Camila Giorgi before winning 8-6 in a deciding set.

"Now I just had to go find her, because I need to tell her some juicy stuff. I just went and searched for her in the training room. "Yeah, I think everything will be normal. And then when we get on the court, it's time to compete. It's go time. Until then, we're the same girls as always."

It is the first time that two American women have reached the last four at Roland Garros since 2002, when Serena Williams beat sister Venus in the final, after a semi-final win over Jennifer Capriati. Stephens, who was ranked 957 just six weeks before her maiden Grand Slam triumph last year after a series of injury problems, is now into the semi-finals of a major for the third time. "To have two Americans in the semi-finals of the French Open, I think, is pretty incredible," said the 25-year-old. "That means one American will be in the final of a French Open, which is another amazing thing. All in all, I don't think anyone can complain."

Stephens and Kasatkina traded breaks early in the match, before the American produced some ferocious hitting at the end of a marathon eighth game to give herself the chance to serve for the opening set. She did just that, with the help of a sumptuous backhand drop shot. The 14th-seeded Kasatkina kicked off the second set with a solid hold of serve, but Stephens broke in the third game with a venomous cross-court forehand and eased to victory after just an hour and 10 minutes of play. Keys struck 30 winners past a battling Putintseva in an impressive display, but will have to at least maintain that level in the last four against Stephens. The 23-year-old struggled nine months ago under the pressure with the US Open title on the line, but she is confident that performance won't affect the match at Roland Garros.

Putintseva made the first significant move with a break in the seventh game on Tuesday, but failed to serve out the set as Keys found her range. The Kazakh showed great resolve to force a tie-break, though, saving two set points on her own serve. But the greater power of Keys paid dividends in the breaker, as the American finally took the opener on her fourth set point with her 18th winner.

Putintseva fought hard at the start of the second set, but Keys broke through to take a 4-3 lead with a rasping forehand return before confidently serving her way to the semi-finals. In the other half of the draw, two-time champion Maria Sharapova will meet 2016 winner Garbine Muguruza on Wednesday, while world number one Simona Halep takes on double Grand Slam champion Angelique Kerber.