LONDON, Nov. 15 -- Six-time champion Roger Federer saved four match points to beat Swiss compatriot Stan Wawrinka to set up a mouth-watering final showdown against world No. 1 Novak Djokovic in the ATP World Tour Finals here on Saturday.

Federer, 33, came back from the brink of defeat to beat third seed Wawrinka 4-6, 7-5, 7-6 (6) in two hours and 48 minutes and head into final for a record-equalling ninth time. x Wawrinka appeared on course to cap a career-best season with a spot in his 17th tour-level final, but he could not convert four match point opportunities in the deciding set at 5-4; then a fourth at 6-5 in the tie-break.

"I got lucky," said Federer. "Stan played better from the baseline and that usually does the job on this court. But I kept fighting.

"It's tough [on Stan] but I'm thrilled to be in another final in London."

Djokovic is on course to become an undefeated champion for a third straight year at the year-end finale. Ivan Lendl, the five-time former titlist, was the last player to clinch three straight crowns from 1985 to 1987.

The two-time defending champion, who also lifted the 2008 trophy, defeated fourth seed Kei Nishikori, the first Asian singles player to compete at the event, 6-1, 3-6, 6-0 earlier.

Djokovic is now unbeaten in his past 31 indoor matches. He dropped just nine games in three round-robin matches prior to his fifth meeting with Nishikori.

In their previous 37 meetings, Federer leads 19-18 but Djokovic has won their last three clashes, including their five-set thriller at the Wimbledon final this year.