Confident Djokovic thinks Nadal's the man to beat at the US Open

World No 1 Novak Djokovic is doing it all these days despite the grilling preparations for the US Open that will start on Monday.

A day after addressing the U.N. General Assembly on Friday at the United Nations and then being involved in the ATP Heritage Celebration, Djokovic was back in more familiar surroundings on Saturday, signing autographs at the Flushing Meadows for the annual Arthur Ashe kids' day.

After practising on the centre court, the Serbian was besieged by autograph hunters then the media as he retreated to the conference room.

Djokovic has played in each of the last three U.S. Open finals, winning the title in 2011, and remains among the favourites this year despite mixed results this season.

He won his third successive Australian Open in January and made the final at Wimbledon, losing to Andy Murray, who also beat him in last year's U.S. Open final.

But the World No 1 thinks that Spaniard Rafael Nadal is the man to beat at the Flushing Meadows.

According to the BBC, Djokovic expressed that Nadal is definitely back and almost playing the best tennis that he has ever played on hard courts.

The Serbian star said that Nadal had also been the best player this year and there was no question about it, looking at the results. Second seed Nadal begins his bid for a second US Open title against American Ryan Harrison on Monday.

But putting things into perspective, Djokovic’s run-up to the US has been solid -- he reached the semi-finals in Montreal then the quarter-finals in Cincinnati.

"I thought I played quite decent in these two weeks," he said.

"Just that both matches that I lost were 7-6 and 7-5 in the third set, and in important moments, I wasn't finding that maybe extra strength to be calm and to play the right shots.

"That's what happens, you know. You go through these periods. But my confidence is still there."

At 26 and with six Gand Sam titles already under his belt, Djokovic is at the peak of his powers and showing no signs of slowing down or waning interest.

"I feel that I'm in my prime in my tennis career and I really want to keep on playing tennis at this level hopefully for years to come," said Djokovic, who plays Lithuania's Ricardas Berankis in the first round.

"As long as I have the desire, as long as my body holds on, as long as, you know, there is this love, flame of love for this sport inside of me."