However, while Sharapova had a tough time rallying from a set down to win 1-6, 6-3, 6-4, Errani swept past her doubles partner and best friend Vinci winning 6-2, 6-4.
In doing so, Errani became the first Italian woman in the Open era to make the semi-finals at Flushing Meadows.
“It’s always hard to play against a friend and it was strange seeing her on the other side of the net,” said Errani, who already has four tour singles titles to her name this year.
“I am happy to get to the final. Can I win the title? I will tell you in three or four days,” added Errani, the 10th seed, who was the French Open runner-up to Sharapova this year. She goes on to face either three-time champion Serena Williams or Ana Ivanovic for a place in the final while Sharapova faces World No 1 Victoria Azarenka.