MARIA SHARAPOVA battled for more three hours in roasting conditions to reach the third round and then called for greater clarity on the tournament’s extreme heat policy.

The third seed was on court for three hours and 28 minutes on her way to a 6-3 4-6 10- 8 victory over Italy’s Karin Knapp.

Tournament referee Wayne McKewen makes the call when to suspend play but there is no fixed temperature that brings the rule into effect, with humidity, wind direction and the immediate forecast taken into account.

Conditions were deemed unplayable as the thermometer hit 42C, yet on Tuesday it was above 40C for five hours and play continued.

Sharapova said: ‘‘There is no way getting around the fact that the conditions were extremely difficult and have been for the last few days.

‘‘It’s a tough call. I think the question I have is no one really knows what the limit is. Not the players or the trainers.

‘‘We have never received any e-mails or warnings about the weather or what to do. Actually, I did receive one while I was in the ice bath a few minutes ago, and I was like, ’That’s a little too late’.’’ Sharapova also argued that the time limit of 20 seconds between points should be extended or suspended when conditions are extreme.

The third seed was given a time violation during the deciding set, and she said: ‘‘Anywhere else, it’s fine. If that’s the speed of the game that’s absolutely fine. But in these conditions, I mean, let it go.’’ Sharapova next meets France’s Alize Cornet, who was in tears at the end of her 6-3 4-6 6-4 win over Camila Giorgi.

Defending champion Victoria Azarenka, Caroline Wozniacki and Agnieszka Radwanska all had the luxury of playing tunder a roof.

Azarenka opened the night session on Rod Laver with a battling 6-1 6-4 victory over Barbora Zahlavova Strycova, who held her own in the second set. Tenth seed Wozniacki beat American Christina McHale 6-0 1-6 6-2 while Radwanska was a 6-0 7-5 winner over Olga Govortsova.