New York:Roger Federer moved within one victory of his fifth consecutive US Open title on Saturday, firing 20 aces to overpower Serbian third seed Novak Djokovic 6-3, 5-7, 7-5, 6-2.
But the Swiss superstar will have to wait until Monday to try and capture his 13th Grand Slam title and move within one of the all-time record total of Pete Sampras.
In a rematch of last year's final, second seed Federer stretched his US Open win streak to 33 matches but rain stopped the other semi-final between world number one Rafael Nadal and British sixth seed Andy Murray.
The 21-year-old Scotsman led 6-2, 7-6 (7/5), 2-3 when his first Slam semi-final was halted until Sunday afternoon, pushing the men's final to Monday afternoon, the first time since 1987 that the Grand Slam event will end late.
"Winning here at the Open would mean a hell of a lot to me," Federer said.
"At the moment the focus is to defend my title and get my fifth. The Pete thing is very much alive and everything is possible, but I would like to focus on the five in a row right now."
Olympic champion Nadal defeated Federer in this year's French Open and Wimbledon finals and the Spanish left-hander replaced him atop the rankings last month, ending a Federer reign of 237 weeks.
"If I win it's great and I'm back in the race and things aren't so bad like everyone is saying," Federer said. "A win would be huge."
By reaching his 17th Slam final, Federer matched Rod Laver for third on the all-time list, one behind Sampras and two shy of Ivan Lendl's record.
Federer is trying to become the first man to win two Slam events five times in a row, having turned the trick last year at Wimbledon, and would be the first man since Bill Tilden in 1924 to win the US title five times in a row.
Federer connected on 76 percent of his first saves and pulled out an ace when he desperately needed it on several key points.
"My serve got me out of trouble a few times," Federer said. "It has been hard all week to break against the wind. It makes quite a difference in how you construct points. I've concentrated quite a bit on my serve and it has helped."
At times, Federer looked and felt like the dominating figure he has been for the past five years.
"I had moments where I thought, 'This is how I normally play on hardcourts.' I had moments where I thought, 'This is how I want to play all the time,'" said Federer. Federer breezed through the opening set in only 25 minutes.
"The way I played the first set was a key moment," Federer said. "He was looking a little tired. I think I broke his will as well when I got the third set. All of a sudden I was playing my best with the lead. I knew I could get it in four."
Australian Open champion Djokovic, 21, would have replaced Federer, 27, as world number two had he won the US Open.
"He was playing good. He deserved to win," Djokovic said. "I was a little disappointed that I wasn't able to give him a challenge. I was just unlucky to lose that third set and it was more or less routine for him in the fourth."
Djokovic netted a forehand to give Federer a break chance in the 11th game of the third set and sent a backhand volley long to hand Federer a 6-5 lead.
Federer made a miraculous leaping forehand save of a Djokovic overhead smash on the next point and held to claim the set.
"In the important moments he served it out really well. He didn't give me a chance because he served well," Djokovic said. "I knew the third set was crucial. If it went my way I had a bigger chance to get the victory."
Djokovic surrendered a break in the fifth game of the fourth set, sent a backhand volley wide to give away another in the seventh, and saw Federer hit a winner to hold and end matters after two hours and 45 minutes.
Federer improved to 7-2 all-time against Djokovic, who ended the Swiss' run of 10 consecutive Slam finals by beating him in an Australian Open semi-final.
Federer has never lost a US open semi-final or final and was last beaten here by David Nalbandian in the 2003 fourth round.
Djokovic was unhappy at playing his semi-final just 31 hours after he went to bed from a night quarter-final, saying, "It's not really the best thing you want to have for yourself. But what are you going to do? I had bad luck."