Novak Djokovic captured his 10th Grand Slam title Sunday at the US Open after Roger Federer once more pushed the world number one him to his highest level.

The 28-year-old Serbian star defeated 17-time Grand Slam champion Federer 6-4, 5-7, 6-4, 6-4 in the final at Arthur Ashe Stadium, pulling level at 21-21 in the greatest current rivalry in tennis.

Ageless wonder Federer, turning back the clock at 34, still hasn't won a Grand Slam since 2012 at Wimbledon after losing the US Open and Wimbledon finals to Djokovic this year.

But he has showed Djokovic the level he must reach in order to win major titles.

"Coming out knowing you are playing against probably the best player in the history of the game adds to the pressure," Djokovic said.

"He's never going to drop his level. I need to produce my best level against him and that's what was needed from me to win this trophy."

Djokovic was serving for the match at 5-2 in the fourth set when Federer broke and threatened again when Djokovic served in the final game before finally falling after three hours and 20 minutes.

"Roger showed why he's a champion, making me play to the last point," Djokovic said. "It was a huge relief when I saw that forehand return go out.

"I'm going to try and enjoy and nurture this victory for as long as I can."

For Federer, who failed to become the oldest US Open champion since Ken Rosewall at 35 in 1970, it was a return to the US Open final for the first time since a 2009 loss to Juan Martin Del Potro, although he could not claim his sixth career crown, and first title since 2008, on the New York hardcourts.

"The rivalry, it has been a good one," Federer said. "It's always tough playing against one another. I think we walk away from it knowing more about our games and about ourselves really."

A day after US Open women's champion Flavia Pennetta dropped in a casual last mention that she was retiring, Federer teased the crowd of 26,420 about his future for a split second before making his plans clear.

"I'm very pleased with where my game is at," Federer said.

"It feels like it has moved in the right direction. I'm back in the final for the first time since 2009. I love the sport. I've got a lot of passion.

"One last thing -- I'll see you guys next year."

No one will be happier for that than Djokovic, who sees Federer as a role model for what he might achieve over the next six years of his own career.

"I have to share my admiration for Roger and everything he's doing for tennis," said Djokovic. "He keeps improving and keeps on going.

"I have a tremendous respect for Roger and what his game is representing for me and for every other player, for everything he has ever achieved."

Djokovic has some impressive achievements of his own, winning three Grand Slam titles in a season for the second time in his career after 2011.

"It has been an incredible season, the second best of my career only behind 2011," said Djokovic, who noted one major difference.

"I'm enjoying this year more than any previous one in my life. Because I'm a husband and a father now, this makes this one even sweeter.

"Results like these give me the motivation to keep going."