An unbeaten Steve Smith has extended his dream Test comeback by rescuing Australia yet again in the Ashes opener at Edgbaston, where the tourists were 3-124 and holding a 34-run lead at stumps on day three.

Smith, having dragged Australia from 8-122 to 284 with a century on day one, was at it again on Saturday as he revived their hopes of setting a competitive target while weathering a bouncer blow to the helmet.

The tourists crashed to 2-27 in Birmingham before Smith, who will resume on 46, steadied with help from Usman Khawaja (40) and Travis Head (21 not out).

Rory Burns missed a chance to run Head out for nine after Smith called his batting partner through for a sharp single in the final session, which ended almost half an hour early because of bad light.

It was the only blemish of note in Smith’s remarkably comfortable stint at the crease, apart from his misreading of a rising delivery from Ben Stokes that hit the helmet.

Team doctor Richard Saw, handed new powers under the concussion-substitute policy that came into effect this week, gave Smith the all clear to continue.

David Warner and Cameron Bancroft both fell cheaply for a second time in their first Test since the sandpaper saga.

But the third member of the Cape Town trio has a chance to make it twin tons in the series opener, one of few achievements Smith is yet to tick off in a Test career stacked with accolades and match-winning knocks under immense pressure.

Two days after Stuart Broad declared his team must get Smith early to reclaim the urn, England quickly turned to defensive fields and leg-slip traps in their attempt to unsettle the fiercely determined batsman.

A couple of balls startled Smith by keeping low but England were otherwise made to look like Wile E. Coyote hunting the Road Runner.

The absence of Jimmy Anderson, who limped through for singles then was unable to bowl because of his calf injury, meant England’s first-innings lead of 90 runs was not as intimidating as it might otherwise be.

Yet Warner and Bancroft’s unconvincing dismissals, to Broad and Moeen Ali respectively, means so much rests on Smith’s restless shoulders regarding the final result.

The right-hander’s fluent knock will build belief among teammates but recent history underlines the enormity of the challenge confronting Australia.

Not since 1981 have the tourists won an Ashes Test in England after conceding a first-innings lead.

England’s first-innings total of 374 would have been a lot lower if not for Broad and Chris Woakes’ 65-run partnership.

The hosts resumed at 4-267 on day three and negotiated the opening half an hour with few concerns before losing 4-18, including two wickets in a single Nathan Lyon over.

England’s lead was just 16 runs when Broad entered the fray.

It ballooned as a desperate Tim Paine reshuffled his fielders with plenty of input from Smith, having also thrown the ball to the former skipper.

-AAP