Dementieva was due to play local Samantha Stosur in the semi-finals of the Australian Open warm-up but withdrew as the on-court temperature soared towards 50 degrees Celsius.

"I was feeling really bad and dizzy and very weak so I think that I'm having all the symptoms of a heat illness," Dementieva told a news conference.

"I couldn't go on the court to do my warm-up. I couldn't even hold my racket."

Under WTA rules, players can request a 10-minute break if the weather reaches extreme levels but the Russian said she was unable to play at all.

"I've never had this before. I've never felt that bad in the past," she said.

"It's been very difficult playing in the peak of the heat, playing singles and doubles at the same time, that was too hard for me."

Dementieva, French and U.S. Open finalist last year, is the latest in a long line of high-profile players who have succumbed to the scorching Australian heat .

In just two days in Sydney, Russia's Nadia Petrova, the world number 13, quit her match against Chinese amateur Peng Shuai on Thursday because of heatstroke, while big-serving American Taylor Dent retired halfway through the first set of his clash with Max Mirnyi after becoming ill.

Players have been demanding for years that the Australian Open, traditionally held in the last two weeks of January, be moved back to March when the weather is cooler and also to give them a longer break.

It's not unusual for some of the top players to miss the first grand slam of the year through injury and this year's absentees include last year's champion Justine Henin-Hardenne, beaten finalist Kim Clijsters [Images] and Jennifer Capriati [Images], the 2001 and 2002 champion.

'NO CHANGE'

However, Tennis Australia president Geoff Pollard insisted the tournament would remain in January.

"To lose a couple of players through injury - which is the only reason we lose them now - is normal and I don't think we're losing any more than the U.S. Open loses where they are tired and the season has been going for too long," Pollard said.

"I'm not certain that you would get any different number of withdrawals in June or March as you get in January."

Opinions among the players remains divided. Australian Lleyton Hewitt [Images] thrives in the heat but says he can sympathise with players who come from colder climates.

"It's tough when they have to come from Europe where it's minus degrees over there at the moment," Hewitt said.

"So to come and expect to play your best tennis straight off the bat under these conditions, it's never going to happen."

But Stosur, who comes from subtropical Queensland, said the heat should not be a problem.

"I can't really understand why there are so many injuries at this time of the year when we've all supposedly had an off-season," she said.

"Any time you play a tournament a week before a grand slam, everybody is a bit careful about what they do.

"But having said that, if you enter the tournament everyone hopes they can go through with it."

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