Two-time grand slam champion Lleyton Hewitt admits it will be tough for Australia to win this year's Davis Cup, but he's ready to give his heart and soul to try to achieve it.

Australia are through to the semi-finals after scraping past Kazakhstan 3-2 in Darwin.

The Andy Murray-led Great Britain await Australia in an away tie in September, and Hewitt knows it will be a tricky challenge for his youth-laden side.

"We're on the tougher side of the draw," said the retiring Hewitt, who is aiming to add to the Davis Cup titles he won in 1999 and 2003.

"Argentina play Belgium in the other half, which is probably the weaker section.

"The last three or four years, Davis Cup has been as big as any grand slam for me personally.

"When I make my schedule, everything has worked around the Davis Cup and trying to get the most out of myself.

"I feel like I can still play a mentor role in the team at the moment, especially on the doubles court.

"These young guys [such as Nick Kyrgios and Thanasi Kokkinakis] are the future of our team, and I'm trying to help them out as much as possible."

Davis Cup captain Wally Masur is confident Bernard Tomic will be able to sort out his beef with Tennis Australia in time to link up with the team for the semi-final.

Tomic was suspended for last week's quarterfinal showdown against Kazakhstan after he unleashed a scathing attack on TA boss Craig Tiley and director of player performance Pat Rafter after his Wimbledon exit.

The world No 25 made more headlines this week when he was arrested in Miami after a loud party.

Masur is doing his best to play peacemaker between TA and Tomic, and is hoping for a resolution soon.

Another challenge facing Masur is getting the best out of Kyrgios, who was meant to spearhead Australia against Kazakhstan.

The 20-year-old was overlooked for the reverse singles rubber on Sunday after suffering a four-sets loss to world No 115 Aleksandr Nedovyesov on day one.

Kokkinakis also suffered a disappointing singles loss, but Masur said his "Special Ks" remained an important part of the team.

"I hope that they realise that no one sits in judgment that they lost a tennis match," Masur said.

"It is part of their tennis journey and it is part of their journey as people."

Hewitt and Sam Groth were the heroes against Kazakhstan.

The pair joined forces to win Saturday's doubles clash, before triumphing in their singles matches on Sunday. - AAP