Australia captain Ricky Ponting believes that putting early pressure on South Africa will be crucial when the two sides clash in the second ICC CWC semi-final here on Wednesday.

Australia have won nine matches in a row at the tournament, including a group match against Graeme Smith's South Africans in St Kitts last month.

"If they play their best cricket they can put us under pressure, so it's necessary to get off to a good start and keep them under pressure," Ponting said on Tuesday.

"Their cricket is similar to ours. They are very aggressive. It'll be an interesting and challenging contest and we are looking forward to the challenge."

Australia are looking to complete a hat-trick, having won the title in 1999 in England and 2003 in South Africa. They are unbeaten in their last 27 ICC CWC matches, a tournament record.

Their last defeat came against Pakistan in a group match in 1999.

South Africa are the only team which came close to beating Australia when they tied their epic 1999 semi-final before bowing out of the tournament on inferior net run-rate.

Ponting said his side had been playing close to their best for more than a month in the tournament and it was important to keep momentum going.

"We have gained a lot of confidence after nine wins in a row, but it all comes down to 100 overs tomorrow," he said.

"We have not let the opposition in right from the first match and have not been challenged as far as closeness of the games is concerned. We have been close to our best."

Australia have so far not faced a serious challenge to their supremacy, but Ponting believed his team again needed to execute the gameplans well to make it to the final.

"Our execution has so far been great and we hope we do it again tomorrow," said Ponting.

"We have been batting well. There are a lot of champion players and I think the side is similar to the one we had in 2003, blend of youth and experience."

The Australian captain was all praise for ICC CWC debutants Shaun Tait and Michael Clarke, saying they had so far done an impressive job.

Middle-order batsman Clarke is the third-highest Australian scorer with 368 runs in nine matches with three half-centuries, while fast bowler Tait is behind only veteran paceman Glenn McGrath with 19 wickets.

"Clarke has an outstanding tournament and he has made the number-four spot his own," said the skipper.

"Tait has been very impressive. Whenever I've called on him to get us a wicket he has done that. He is still finding his feet at international level, but he has been a wicket-taker in middle overs."

McGrath, playing in his last ICC CWC, is the tournament's leading wicket-taker with 22 in nine matches.

"He (McGrath) keeps it pretty simple whether it's action or approach.

He keeps delivering and it's unbelievable," said John Buchanan, who is stepping down as Australia coach after this tournament.

"Right now we are focusing on one game. We want to play our best cricket tomorrow and win and then have a chance to play another match. The aim is to play a perfect game," said the Australian coach.