"Everybody can think what they want to think. Everybody has the right to think and believe that they are the best in the world. We are professional athletes," Jankovic said.

"You know I'm the No 1 player in the world, and I believe I'm the best one. I feel as the No 1 player in the world. Serena can feel the same.

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"Everybody has, you know, their own confidence and the belief in themselves. I don't think you could be successful if you think somebody else is better than you and you're not good enough to be here."

However, Jankovic admitted she was keen to seal her first Slam here to silence critics who point to her failure so far on the big stage.

"It would be nice," she smiled, adding that she wanted to win all four majors.

"My dream is to win all four of them, you know. I want to play well on all surfaces. This is something that I want. This is something that I want to achieve. We will see if that will happen."

Nine-time Slam winner Williams today said she had "nothing against Jankovic" but still backed herself as the best player on tour.

"I said that I feel like I'm the best player, because I would feel weird sitting here saying I'm not the best," she told journalists.

"Even if I'm ranked 100 in the world, I would sit here and say I'm the best player."

Jankovic added that she had recovered from the bout of flu that forced her out of an exhibition event in Hong Kong and would be ready for her first-round match against Austria's Yvonne Meusburger.