Australia 2 for 193 (Khawaja 91*, Warner 56) trail England 346 (Root 83, Malan 62, Cummins 4-80) by 153 runs
Sydney: Australia laid a platform from which they can take control of the final Ashes Test against England on the second day in Sydney Cricket Ground on Friday.
Usman Khawaja's unbeaten 91 took the home side to 2-193, 153 behind.
Khawaja shared stands of 85 with David Warner, who made 56, and an unbroken 107 with captain Steve Smith, ominously placed on 44 not out.
England earlier moved their overnight 5-233 to 346 all out in an action-packed morning session.
After Dawid Malan fell for 62, Moeen Ali chipped in with 30 before some edging, swiping and the occasional meaty blow brought Tom Curran 39 and Stuart Broad 31.
Pat Cummins, bowling with hostility, ended with 4-80, but he and Josh Hazlewood were both guilty of awful dropped catches off Curran and Moeen respectively.
Australia, who have already sealed the Ashes and lead the series 3-0, are looking to extend England's winless run down under to 10 Tests.
On a pitch that remains excellent for batting, albeit showing consistent signs of turn, they have the opportunity to get up to and beyond the tourists on Saturday.
England's hopes of running through the Australia top order would have been raised by Broad finding a gap between Cameron Bancroft's bat and pad in the second over after lunch, only to be snuffed out by Khawaja, Warner and Smith.
The touring bowlers did little wrong on a surface that looks to be losing its pace and bounce. New-ball pair James Anderson and Broad went through their skills to provide a constant threat, while debutant leg-spinner Mason Crane looked capable of causing problems.
Warner, who had made centuries in his past three Tests in Sydney, looked primed for another when playing flowing cover drives. It took a clever off-cutter from Anderson to find the edge of the opener's bat.
Khawaja, out of sorts at first, played the supporting role in his partnership with Warner, but gradually became more comfortable in the company of Smith. The left-hander played square of the wicket on both sides and lofted the spinners down the ground - his half-century was reached with a straight six off Moeen.
It is the continuing presence of Smith, who has already made three centuries in the series, that is of most concern to England.
On 26, the skipper edged Broad past diving wicketkeeper Jonny Bairstow but, for the most part, was in to his familiar, infuriating work of nudging the ball behind square on the leg side.