Steve Smith racked up another milestone as he continued to torment England and Usman Khawaja neared a century to put Australia in a strong position after day two of the final Ashes Test in Sydney on Friday.

The Australian skipper became the second fastest batsman to reach 6,000 Test runs in his 111th innings, second only to the legendary Don Bradman.

Smith, with three centuries in this five-match series, has been the bane of the England team and was potentially heading towards another ton.

At the close, Smith was on 44 with Khawaja reaching his highest score of the series on 91 in Australia's 193 for two in reply to England's 346 first innings.

"We're stoked he's on our team so we don't have to bowl at him," Ausralia paceman Pat Cummins said of Smith.

"Those big innings he has played have been really important. In Brisbane and Perth they were match-winning and in Melbourne it was match-saving.

"It's just incredible and I think he's been the difference between the two sides."

So far in the series Smith has scored 648 runs at 162.

The pair shared in a 107-run partnership after the loss of openers Cameron Bancroft and David Warner.

Khawaja raised his third fifty of the series with a six down the ground off Moeen Ali.

SCORES IN BRIEF

ENGLAND: First innings 346 (Cook 39, Stoneman 24, Vince 25, Root 83, Malan 62, Moeen 30, Curran 39, Broad 31; Starc 2-80, Hazlewood 2-65, Cummins 4-80)

AUSTRALIA: First innings 193 for 2 (Warner 56, Khawaja 91 not out, Smith 44 not out; Anderson 1-25, Broad 1-28)