NEW YORK (AP) — Roberta Vinci has continued the best Grand Slam tournament of her career by ending Serena Williams' string of major championships.

Williams was trying to become the first player since Steffi Graf in 1988 to win all four Grand Slam events in the same year. Instead, she was beaten by the unseeded Vinci in the U.S. Open semifinals, falling 2-6, 6-4, 6-4.

The defeat of Williams is one of the greatest upsets in tennis history. The 43rd-ranked Vinci had never won a set off the 21-time major champion in four previous meetings and was in her first career Grand Slam semifinal at age 32.

Her victory sets up an all-Italian final between Vinci and Flavia Pennetta, who upset second seed Simona Halep 6-1, 6-3.

Sunday's men's final will include top seed Novak Djokovic, who needed just 85 minutes to knock out defending champion Marin Cilic, 6-0, 6-1, 6-2. The nine-time Grand Slam champion dropped just 11 points in the first set and improved to 14-0 all-time against Cilic.

Also reaching the men's final is 34-year-old Roger Federer, who saved all four break points he faced in a 6-4, 6-3, 6-1 rout of No. 5 Stan Wawrinka. The second-seeded Federer still hasn't dropped a set in the tournament after winning 80 percent of his first serve points and limited himself to only 17 unforced errors.

The 17-time Grand Slam winner is seeking his first major title in more than three years and his first U.S. Open crown since 2009.