New York, Sep 12 (IANS): World No.1 Serena Williams saw her dream of a calendar year Grand Slam evaporate as Italy's Roberta Vinci shocked the American to reach the US Open women's singles final against compatriot Flavia Pennetta here.

Vinci battled back to stun the three-time defending champion 2-6, 6-4, 6-4, ending Williams' 33-match US Open win streak and 27-match Grand Slam winning-run on Friday, reports Xinhua.

In Saturday's final, Vinci will face 26th-ranked compatriot Pennetta, who upset Romanian second seed Simona Halep 6-1, 6-3, in the first all-Italian Grand Slam women's final in the Open Era.

"She played out of her mind. I don't think I played that bad. She just played really well. I don't want to talk about how disappointing it is for me. If you have any other questions, I'm open for that," said Williams in a briefer-than-usual news conference.

Vinci was overjoyed by her shock win. She said she never expected to win after losing four prior matches against Williams without taking a set.

"It's an incredible moment for me. It's like a dream. I'm in the final. I beat Serena. It's the best moment of my life. When I wake up, I say, 'I have a semifinal today. I play Serena. Try to enjoy.' I didn't expect that I would win," Vinci said.

In the match-up of first-time Slam finalists, Vinci has a 4-5 career mark against Pennetta, who took just 59 minutes to dispatch Halep.

"It's amazing. I didn't think to be so far in the tournament. I played really well. I tried to play every match the best I can from the first one. Don't worry about the draw and focus on the things I have to do on the court and here I am," Pennetta said.

"Will be a tough match for both. It will be a lot of pressure. We know each other for a long time. I will do my best. But I will like to play, enjoy and play my game," Vinci said of the final.