On a day which brought temperatures in the low 40s in the shade and 10 degrees hotter on the field, the Australians declared late in the day at 527 for five, with Gilchrist not out on 102 after belting the second fastest hundred in Test history from just 57 balls.

Trailing by 556 runs, England were already in trouble in their second innings at 19 for one at stumps, with Ian Bell not out on nine and Alastair Cook on seven.

England opener Andrew Strauss again failed, adjudged lbw for a duck padding up to Brett Lee from the fourth ball of the innings.

The Australians, already 2-0 up in the series, would regain the Ashes with victory here.

Despite their dominant position Gilchrist said the Australians still weren't discussing the possibility of regaining the Ashes in Perth.

"It hasn't been spoken about," he said.

"If guys are doing it, they are doing it on their own. We have nine wickets to get, we are in a good position and it is very exciting and we've fought hard. But it certainly hasn't been spoken about."

Besieged England coach Duncan Fletcher said his side had squandered a great chance on the second day, but that they had to fight over the last two days of the match.

"Practically, it is a very, very difficult challenge, but the individuals have to come here and show what they are worth," he said.

"They have to make sure they pitch up tomorrow in a positive frame of mind."

Mike Hussey, Michael Clarke and Gilchrist all made centuries in the Australian second innings, the latter launching an extraordinary assault on the tiring England bowlers late in the day to burst out of his Ashes form slump.

Gilchrist reached his half-century in 40 balls and then took just another 17 to reach triple figures, with 12 fours and four sixes, and in doing so replicated Doug Walters' famous century in a session in 1974 at the same ground.

After reaching 50, Gilchrist thrashed four sixes from the next six balls he faced as Viv Richards' record of a century in 56 balls came under threat.

Panesar went for 24 runs in one over, an unwanted Ashes record for a player who claimed three wickets in the second innings to have eight for the match.

Gilchrist, who has enjoyed a lean time with the bat in the last two Ashes series, seemed certain to break the record, but was ultimately denied by England seamer Matthew Hoggard.

When Ricky Ponting declared Australia's innings closed, Clarke (135 not out) and Gilchrist had added 162 in 98 minutes.

Clarke reached his century in 130 balls, with 13 fours and one six.

Hussey, controversially overlooked during the entire 2005 Ashes series in England, continued his incredible run at the top level when he notched his maiden Test century against England and his fifth overall.

The left-hander pulled the unlucky Harmison straight down the ground for his 12th four to bring up the milestone in 213 minutes from 148 balls, but was caught behind off the bowling of Panesar from the last ball before tea.

Hussey had enjoyed a fair slice of luck, as he was lucky to be given not out on 15 and was dropped twice.

It was a horror day in the field for the English, who showed great spirit but could only watch the Ashes slipping away as they not only bowled without luck, but had to contend with energy-sapping heat.

A number of catches went begging, Geraint Jones missed a stumping and confident appeals were turned down as they claimed just four wickets on the day.

Earlier, opener Matthew Hayden missed out on a century when he fell for 92, while Australian captain Ricky Ponting passed the 500-run mark in the series in making 75.

Highlighting the enormity of the task facing England, the highest successful fourth innings run chase at the WACA is 342, when Australia beat India back in 1977.

In further bad news for the tourists, spinner Ashley Giles had to leave the tour because of an illness to his wife. He was replaced in the squad by all-rounder James Dalrymple.