Venus Williams is set to meet Kim Clijsters in the semi-finals of the US Open after beating French Open champion Francesca Schiavone.

The American is playing for the first time since Wimbledon because of a knee injury and overcame the windy conditions to claim a 7-6 (7-5) 6-4 win.

Kim Clijsters was relieved to emerge from her match against Samantha Stosur, but said she might not be so fortunate in her match with Williams.

"I didn't play a good match, but I was obviously able to win it," the defending champion told reporters after a mistake-marred 6-4 5-7 6-3 win over fifth-seeded Australian Stosur.

"The next match everything will have to be a lot better," said Clijsters, who registered 43 unforced errors. "My serve hasn't been going the way that I want it to go.

"I think it's because when I play players who play aggressively, I tend to not finish off my service motion properly."

She added: "In my movement, as soon as I land on my left foot, which normally you're supposed to land forward, I'm already pushing off to try to get to the next shot. I know that that's not what you're supposed to do."

Williams and Clijsters have split 12 career meetings with Clijsters winning the last four, including two wins at the US Open.