World number one Victoria Azarenka repeated her Australian Open triumph over Maria Sharapova to reach her first US Open final.
The Melbourne victory, which gave Azarenka her first grand slam title, had been one-sided as the Belarusian lost only three games but this was a titanic struggle between two of women's tennis' biggest fighters.
Azarenka finally came out on top 3-6 6-2 6-4 after two hours and 42 minutes and will meet Serena Williams in the final.
The 23-year-old said: "I was just trying to grab the first opportunity that I had. Maria is such a great player. I knew she would come out firing and she did. I tried to find my rhythm and just fight.
"I tried to give whatever it takes. I knew my opponent was going to play hard so I had to play harder. I gave it my all. I guess it worked. It's my first final and I'm so excited."
Sharapova viewed the match as a missed opportunity and felt her failure to push Azarenka harder in the deciding set cost her.
She said: "It's frustrating, but it's the game of tennis. There were a lot of swings in the match today. I certainly had the lead and the advantage.
"She picked up her game. In the third I think a lot of it had to do with the returns. I didn't do much on her service games. She was winning them pretty easy.
"On mine they were quite long and I was just making too many errors and not putting any pressure on her. So I think that's the most frustrating part."