Justin Langer says Australia must raise their game if they want to retain the Ashes during the fourth Test against England.

The series resumes at Trent Bridge on Thursday with the teams locked at 1-1. But an Australia victory in Nottingham would leave them one-up with one match left in the five-Test series and ensure they retain the Ashes, which have been in their possession since 1989.

After watching England win the second Test at Edgbaston and seeing them held off by a last-wicket stand at Old Trafford, Langer said Australia faced plenty of hard work in their biggest challenge in years.

"We want to win the Ashes or, at least, we don't want to lose the Ashes," he said. When asked about a lapse in Australia's intensity he replied, "I would suggest it hasn't been at the cut-throat edge that we're used to playing at. We've played periods of very good cricket, but in Test match cricket, particularly when you play good teams like England, you cant afford to be just playing it in periods. We've talked about that a lot. We know that we have to increase the intensity throughout the whole series, from the day of the last Test ... through to the last ball of the series."

Langer said that with the express paceman Brett Lee already in the team, Australia needed to think carefully about whether they also wanted Shaun Tait in the side instead of Jason Gillespie. "It's really important, you always talk about balance," he said. "You've got someone like Brett Lee in your side, who's an out-and-out strike bowler, and he's got the pace - you've got to be careful you get the balance right. We've been lucky we've got two of the best ever at the other end [Glenn McGrath and Shane Warne], but no doubt the big question will come down to balance rather than talent in the next few days.

"I've always said Michael Kasprowicz is the hardest bloke for me to face in domestic cricket in Australia. He always tends to go across the left-hander. I've always found him a handful in first-class cricket, as I do in the nets."

But Langer said he had also been impressed by Tait. "He's a bit like Shoaib Akhtar or, in a way, Brett Lee. You need the courage to stand still facing him, he's a different sort of bowler. When he's bowling that fast and he's bowling yorkers like he can, he's obviously a real strike bowler and a great prospect."