Defeats don't dim Novak Djokovic's confidence for US Open

World number one Novak Djokovic could not reach the final of his two US Open tune-ups, but he likes his chances to reach a fourth consecutive US Open final.

The 26-year-old Serbian star, who won his fourth Australian Open title and sixth Grand Slam crown earlier this year, fell to eventual winner Rafael Nadal in a French Open semi-final and to Britain's Andy Murray in last month's Wimbledon final.

Since then, however, he has fallen to Nadal in a Montreal semi-final and John Isner in a Cincinnati quarter-final.

"I thought I played quite decent in these two weeks, just that both matches that I lost were 7-6 or 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," said Djokovic.

"That's what happens. You go through these periods. But my confidence is still there. This is a Grand Slam, so it is different from any other event."

While he has not won a title since April on Monte Carlo clay, Djokovic has not lost confidence in the form that put him atop the tennis world.

Djokovic reached his first Slam final at the 2007 US Open, losing to Roger Federer. He lost to Nadal in the 2010 US Open final, beat Nadal in the 2011 final rematch and fell last year to Murray.

"Last year was a very interesting match, a very close match from two sets down coming back and playing a fifth against Murray and 2010 against Rafa was also close," Djokovic said.

"When I play Rafa, Roger, Andy, it's very few points that really decide a winner. You can't really say who is the clear favorite, because it always goes down the wire who is going to win it. That's the beauty of the sport. That's the beauty of the rivalries we have at the present moment."

Djokovic practiced after a hectic Friday that saw him speak to the United Nations and join a gathering of men who had all reached world number one.

"It was an unbelievable day," Djokovic said. "I was blown away by these wonderful opportunities, that I got personally to speak at the UN in the name of the global family of athletes.

"I know that many big world decisions are made at that place so I had a feeling all of us who came, we were part of something really big, so it was a fantastic occasion."

Asked what impact he might have on the world's needs, Djokovic cited his charity foundation, saying, "Through the charity work, I see myself doing a lot for the world, and for kids especially."

He capped the day by meeting with the only other men who could truly understand the effort needed to become the top tennis player in the world.

"It was a spectacular experience just sharing the same stage with all these legends," Djokovic said. "It was a fantastic and unforgettable experience. I will cherish it and remember it forever."