Serena Williams suffered one of the greatest shocks in tennis history as unseeded Italian Roberta Vinci ended the American’s hopes of a calendar grand slam with a stunning victory in the US Open semi-finals.

Vinci, ranked 43rd in the world, had never gone further than the quarter-finals of a major tournament before but the 32-year-old came from a set down to beat Williams 2-6 6-4 6-4.

It means Williams’ run of 33 consecutive grand slam victories comes to an end while Vinci will now play fellow Italian Flavia Pennetta in Saturday’s final.

After wrapping up her momentous win, Vinci broke down in tears, dumbfounded as she struggled to speak during her on-court interview.

“It’s an incredible moment for me,” Vinci said.

“It’s like a dream, I’m in the final, I beat Serena, it was an incredible match. When I served I was like voooooo, it was impossible.

“I tried to stay focused, not to think about the match or about Serena, she is an incredible player. It is the best moment of my life.”

Vinci added: “I am sorry for the American people, for Serena, for the grand slam, but today is my day, sorry guys.”

Vinci had been knocked out in the first and second rounds at all three major tournaments this year but after a slow start, the wily Italian unsettled her opponent with slice, angle and variety of shot.