SYDNEY: England's problems mounted as Australia took a grip on the fourth Ashes Test, reaching 209 for three at lunch on the second day at the Sydney Cricket Ground on Thursday.

Skipper Joe Root fumbled a good chance off Usman Khawaja on 28 and key all-rounder Ben Stokes left the field with a side strain after bowling four overs.

It just added to England's plight as Steve Smith and Khawaja batted through the extended morning session, punctuated by three rain interruptions of varying durations.

By lunch, Smith was threatening a big score on 51 and Khawaja providing stoic support on 39.

A big moment came for England nearing lunch when Root fumbled an edge off Khawaja from the bowling of spinner Jack Leach.

Khawaja's nick deflected off wicketkeeper Jos Buttler's gloves but Root at slip had time to react and get his hands in the right place. But the chance went begging, much to Leach's anguish.

Compounding the let-off, Stokes pulled up in the next over clutching his left side after bowling a short-pitched delivery to Smith and immediately left the field for treatment.

Along the way Smith became Australia's seventh-highest Test run-scorer, passing current team coach Justin Langer's 7,696 runs. At lunch he was on 7,718.

Smith was proving a major thorn again for England's bowlers as he chases his 28th Test century and 12th in the Ashes.

Khawaja, playing his first Test since the 2019 Ashes series in England for Covid-isolated Travis Head, was unflappable and sharing in a 92-run stand with Smith to wrest the initiative away from England.

The tourists, who grabbed the wickets of Marcus Harris and Marnus Labuschagne late on the opening day to have the Australians at 126 for three, could not make the breakthroughs they were seeking to build on their position.

The Ashes are already gone for England after going down by an innings and 14 runs inside three days in the third Test at Melbourne to give Australia a 3-0 lead with two Tests to play.