Brisbane:Australia vice-captain Michael Clarke remains in doubt for the first Test against England, with a decision on his availability likely to wait until the morning of the game.
Clarke is suffering from a back injury and skipped training on Monday before taking part in some drills Tuesday, with the Ashes series to begin in Brisbane on Thursday.
Australia captain Ricky Ponting has doubts over whether Clarke can prove his fitness but said in the case of "someone as important to our team as he is, we'd probably wait until Thursday morning."
Uncapped batsman Usman Khawaja trained with the team Tuesday and is on standby.
Clarke had to show some signs of improved fitness during the Australian team's training session at the Gabba Ground on Tuesday to have a chance of playing in the first Test of the five-Test series.
"He's been in this situation a few times in the last couple of years, he's had these niggly things with his back and been able to come up most times," Ponting said.
"If we don't see him bat (Tuesday) then it will be hard to see him considered for the game."
Clarke has battled a degenerative back condition for much of his Test career. The condition flared while he played in a domestic first class match for New South Wales 10 days ago and forced him to miss last week's round of the Sheffield Shield competition, which would have been his last Ashes tuneup.
England has no injury concerns around any of its prospective Test players.