Roger Federer celebrated reaching a 22nd consecutive Grand Slam semi-final but only after being made to work for his US Open victory by 12th seed Robin Soderling.
Soderling won a rare set but Federer continued his unbeaten streak against the Swede to march into a semi-final against fourth seed Novak Djokovic.
Five-time defending champion Federer had taken an 11-0 career record over 12th seed Soderling into this night match, their most recent two meetings coming at Wimbledon and in the French Open final.
The world number one made it a round dozen in victories over the Swede, reaching the last four after extending his unbeaten run at Flushing Meadows to 39 matches, Djokovic having earlier beaten 10th seed Fernando Verdasco.
It was not achieved without a fight, however, Soderling looking down and out after two one-sided sets but then making Federer work for the 6-0 6-3 6-7 (6-8 ) 7-6 (8-6) victory in two hours 33 minutes.
"This feels great," Federer said. "It was so close towards the end and it's just a great relief to come through because Robin just got better and better as the match went on.
"I knew it was going to be tough but the beginning was a bit too easy and all of a sudden he found his way into the match and showed what a great player he really is."
Federer could not account for the way the match had shifted away for him having taken a two-set lead in just 59 minutes with some crisp, clean-hitting tennis.
"I don't know, I had a really good start, it was cold so I felt at home being from Switzerland but then it got even cooler and him being from Sweden I think that played in his favour," Federer joked.
"I thought it was a great match towards the end. I got off to a flier but I'm happy I still got through in the fourth."
Of stretching his record of consecutive Grand Slam semi-final appearances, Federer added: "It's not (a record) I aimed for, that's for sure but it's probably one of the greatest records for me in my personal career.
"I'm just happy it keeps on going. I'm healthy and I guess that's most important because that's what has allowed me to play well at majors and I'm in for a shot again to defend my title so that's fantastic."
Of his forthcoming meeting with Djokovic on Saturday, the third year in a row they have met at Flushing Meadows, Federer said: "We've played each other the last two years, semis last year, finals the year before and we've seen what a great player he is on hard courts.
"I'm sure it's going to be a tough match, I'm looking forward to it."
Djokovic was delighted to have reached the US Open semi-finals for the third year in a row as he moved past 10th seed Verdasco in four sets, particularly as it was his first grand slam semi of 2009.
The fourth seed from Serbia beat his Spanish rival 7-6 (7-2) 1-6 7-5 6-2 on Ashe during the day session and will play Federer for the third year in a row at the final grand slam of the season.
Djokovic had reached his first grand slam final in 2007 before going down in straight sets to Federer, while the pair met in last year's semi-finals in New York, with the Swiss star needing four sets to beat the young pretender.
"It feels great," Djokovic said of his achievement. "I haven't done that in the past three grand slams this year, so mentally it was very important for me to overcome today's challenge and to be able to win quarter-finals and to get to the semi-finals for the first time in the grand slams in 2009."
Speaking before the Federer-Soderling match, Djokovic spoke about the possibility of facing the world number one again on Saturday.
"If I play with Roger, we don't need to talk a lot about him: his records in the US Open, we all know his style of the game.
"I have been playing against him many, many times and a lot of different kind of surfaces. There are no secrets in each other's game, so it's a matter of having a good day.
"I hope I can have a good day and concentrate, and physically I'm going to have enough time to recover and be ready."