Roger Federer is now one win away from retaining his title at the ATP World Tour Finals after a 7-5 6-3 success over David Ferrer and is into his 100th career final.
The Swiss former world No.1, looking to triumph in the season-ending tournament for a record sixth time, extended his unbeaten record against the Spaniard to 12-0.
Ferrer did make the fourth seed work in a first set that lasted the best part of an hour, but his exhertions from the previous night, when he lost to Tomas Berdych in three, left him struggling to live with Federer.
The defending champion extended his winning streak to 16 matches and made it nine victories in a row at the end-of-season showpiece, while the result means he will retake third place in the rankings from Andy Murray next week.
"Obviously I'm very happy to have played so well again. That's what it takes to beat David, he's had an amazing season and an amazing tournament," said Federer afterwards.
"He can still win the Davis Cup next week so I hope he does that."
Federer will now face the winner of the semi-final between Jo-Wilfried Tsonga of France and Czech Tomas Berdych on Sunday.
But it was not a vintage display from the Swiss ace, who was edgy in the first set in particular despite his perfect record against Ferrer.
Ferrer returned to the court less than 16 hours after the end of his loss to Berdych and he was in trouble when he began the fifth game with two double faults, but a sharp volley helped him stave off a break point.
Federer had the luxury of a day off on Friday but he seemed to be feeling the pressure and was snatching at shots and making a host of unforced errors.
He survived a game of five deuces, serving to stay in the set at 4-5 and in the next game the 30-year-old moved up a level, winning a fine rally to force two break points, taking the second when Ferrer overcooked a forehand.
That should have been a weight off Federer's shoulders and he served out the set with relative ease.
The Swiss then made the perfect start to the second, his forehand suddenly looking much more secure as he extended his winning streak to four games with a return thumped down the line.
Ferrer was not about to throw in the towel and he stopped the rot by holding for 1-2 with a scrambled backhand winner that said everything about the Spaniard's tenacity.
He then saved two break points to stay just about in the match but it was all over when Federer broke again in the final game, his attacking play finally overwhelming Ferrer.