New York, Sep 6 (IANS): American Serena Williams was in devastating form against Russian Ekaterina Makarova in the women's singles semifinals of the US Open, storming to a 6-1, 6-3 victory and setting up a final clash against Denmark's Caroline Wozniacki.

In an earlier semifinal Friday, Wozniacki beat China's Peng Shuai after the latter retired while trailing at 6-7(1), 3-4, reports Xinhua.

Williams finished her match with 24 winners in 59 minutes, that's about one winner every two and a half minutes. With just 15 unforced errors to go along with those, it was a lethal combination.

Makarova, who was playing her first Grand Slam semifinal, was extremely gracious in defeat.

"Serena, she's a great, unbelievable player," the No.17 seed said. "It's always so tough to play against her. Today she was so aggressive. Maybe I didn't think she would be that aggressive. Like she's just coming so early, so sometimes I was too late because she was too fast."

"She's just born for tennis," Makarova added. "Kind of like Federer, I think."

In the other semifinal, Wozniacki won over Peng after more than two hours of gruelling rallies and high drama.

While trailing Wozniacki at 3-4 in the second set, Peng left the court to seek treatment -- at the time believed to be for cramping -- and play was held up for 10 minutes.

Then the 28-year-old Chinese star returned and played a few points before collapsing to the ground. Peng was finally taken from the court in a wheelchair in agony and in tears.

The official reason for Peng's retirement was confirmed later as heat illness.

"The weather was very hot, my body was hot too, and I started to get cramps, it's really hurting, I could't even move on the court. So the doctor said to me, 'You are not able really to go out to fight and compete, because you don't look well'. But I said, 'No, no, no, I don't want to give up. I want to try one more time'," Peng explained at the press conference which was postponed for three hours.

"And then I come back. I know I'm not going to stay too long, but I just wanted to try to challenge her one more time," she added.

"It's definitely very difficult," Wozniacki talked about the match. "You're out here and you want to battle and finish it off properly, but I just feel very sorry for Peng, because she played really well."

Five years ago, Wozniacki was propelled to superstardom with a run to the final here, falling to Kim Clijsters. And now, in the same tournament, she's reannounced herself on the Grand Slam stage.

"It's incredible. I have goosebumps right now," she said.

Facing up to an awe-inspiring Williams, the Dane looked upbeat.

"She's obviously a great player. She's won so many Grand Slams. She's a good friend of mine, too. I don't want to jinx her now, because she's obviously a tough opponent. When she's on fire, she's hard to beat. But I've had two tough matches against her the last few weeks. I was really close."

"Hopefully for me that would be third time's the charm."

Williams is a win away from her sixth US Open title, which would tie her with Chris Evert for most in the Open Era. She would also become just the second woman, also after Evert, to win three or more US Opens in a row -- Evert actually went on to win four consecutive US Open titles between 1975 and 1978.

"I definitely expect another close match," Williams said. "Wozniacki really knows my game and knows how to play. She's so consistent. I think that's one of the things that makes her really tough. So I just have to be ready and just stay calm and be able to relax and be happy."