Eyeing an unprecedented hat-trick of World Cup titles, champions Australia will be keen to shatter South African hopes yet again when the teams meet in the semi-final on Wednesday.

Top-ranked Australia hold the upper hand as they are unbeaten in 27 World Cup matches dating back to 1999 and also defeated South Africa earlier in the tournament.

The winners will face Sri Lanka in Saturday's final in Barbados after they crushed New Zealand by 81 runs in the first semi-final on Tuesday.

Ricky Ponting's men are aiming to reach their fourth successive final but are braced for their sternest test yet in a repeat of the 1999 semi-final, when Australia forced a dramatic tie before going on to lift the trophy.

"Both teams are very aggressive and up for a fight," Ponting said on Tuesday. "That is what makes Australia versus South Africa very interesting and enjoyable.

"We need to start the game off well and keep South Africa under pressure."

In their group clash last month, Australia won by 83 runs even though at one stage South Africa looked well set for victory on 160 for no loss before a stunning run-out by Shane Watson changed the direction of the contest. 

Struggling South African strike bowler Makhaya Ntini is expected to be left out of the team for a second successive game.

Ntini, 29, has claimed only six wickets in seven games at almost 50 runs apiece. South Africa are debating whether to include left-arm spinner Robin Peterson.

South Africa's biggest challenge would be to avoid suffering the same fate as in their previous campaigns.

As well as the 1999 tied match debacle, when Australia advanced to the final thanks to their better record in the previous round, South Africa were also knocked out in a rain-hit semi-final against England in 1992.

A controversial rain rule reduced their target from 22 runs from 13 balls to an impossible 21 from one.

"It's all about absorbing pressure and applying pressure," coach Mickey Arthur said. "The team that can do that for the longest is going to be the team that is going to win."