Former world number two Svetlana Kuznetsova defied sweltering heat that earlier prompted Agnieszka Radwanska to suggest it was too hot to play to beat seventh seed Caroline Wozniacki on Tuesday in the second round of the Sydney International.

Russia's Kuznetsova, a two-times Grand Slam champion who was knocked out in the first round in Auckland last week and had to qualify for the main draw in Sydney, beat the former world number one 7-6 1-6 6-2 in a match that lasted almost four hours.

Caroline Wozniacki of Denmark receives air from a fan during a ten minutes break due to high temperatures during her women's singles match against Svetlana Kusnetsova of Russia at the Sydney International tennis tournament, Jan 8, 2013. The Australian Bureau of Meteorology reported a temperature high of 41.1 degrees Celsius (106 F) at Sydney's Olympic Park where the tournament is being held. [Photo/Agencies]

Sydney had been forecast to hit a maximum of 43C on Tuesday as Australia swelters in a heatwave that has sparked raging bush fires.

The Australian Bureau of Meteorology reported a temperature high of 41.4 C at 1530(local) at Sydney's Olympic Park and women's top seed Radwanska had said earlier that play should have been abandoned until the temperature dropped.

The world number four, who was given a bye into the second round, played the opening match on center court and beat Japan's Kimiko Date-Krumm 6-4 6-3 to advance to the quarterfinals but even that early in the day the heat was effecting the players.

"I think this is too hot to play tennis," Radwanska told reporters. "Even for players, for ball kids, for the people sitting out there, I think it's just too hot."

"Today was one of the hottest day I (have) played for sure."

Li Na of China hits a return to Ayumi Morita of Japan during their women's singles match at the Sydney International tennis tournament in Sydney, Jan 8, 2013. [Photo/Agencies]

Former French Open champion Li Na, who followed Radwanska on to court, compared the heat to playing in a sauna, but she was good enough to speed through Japan's Ayumi Morita 6-1 6-0 in 52 minutes.

"I was feeling, I don't know, just feeling like unbelievable. They say it was 40, but even on the tennis court even more," Li said.

"I mean, even didn't finish the match, just finish (the) first set (and) I was feeling my feet already burning."