MELBOURNE, Australia (AP)

Serena Williams was having what she called an "out-of-body experience" yesterday in brutal heat at the Australian Open.

Closing the Rod Laver Arena roof and cranking up the air conditioning helped the defending champion pull herself together and advance to the semi-finals - but left her opponent steaming.

"I felt I was watching someone play in a blue dress and it wasn't me, because it was so hot out there," said the second-ranked American, who beat Russia's Svetlana Kuznetsova 5-7, 7-5, 6-1. "And I kept trying to tell myself that it's not hot. But it got hotter."

Williams, seeking her fourth Australian title and 10th Grand Slam championship overall, next faces Olympic gold medallist Elena Dementieva, who had to play her entire match with the roof open. The fourth-seeded Dementieva ousted Carla Suarez Navarro 6-2, 6-2 to run her winning streak to 15 matches after she won two tune-up tournaments.

Top-ranked Rafael Nadal won his fifth match without dropping a set by beating Gilles Simon 6-2, 7-5, 7-5, though he was strongly tested by the sixth-seeded Frenchman.

His victory set up an all-Spanish semi-final, with 14th-seeded Fernando Verdasco - the lowest-ranked player to reach the quarter-finals - earlier beating No. 5 Jo-Wilfried Tsonga, last year's runner-up, 7-6 (2), 3-6, 6-3, 6-2.

The heat wave is forecast to continue today. If Williams wins - Dementieva has won their last three meetings, including the Olympic quarter-finals - she would play a Russian for the third consecutive match in the final. Third-seeded Dinara Safina is facing fellow Russian Vera Zvonareva in the other semi-final.

"Me against the Russians, I guess," Williams said.

With temperatures soaring to 43 C (109 F) on a cloudless day - moths were dying within seconds of touching down on the blistering surface and Williams had her rackets restrung during her match because they lost their tension - the retractable roof was closed after Kuznetsova won the first set.

The heat was beginning to take a toll on Williams, and the eighth-seeded Kuznetsova was angry at the decision. She felt that the break gave Williams time to recover and that playing indoors benefited the American's powerful serve.

"Why should I not be?" Kuznetsova said. "Game going my way. I was very comfortable playing outside. It's two different games. One you play inside; one you play outside. Serena was tough. She's playing great. I give her credit. But I don't get this rule."