Australia captain Ricky Ponting has ominously warned the rest of the World Cup hopefuls they are saving their best until last.

Reigning champions Australia are seeking an unprecedented third consecutive title in the Caribbean and extended their winning streak to 24 World Cup matches on Sunday by beating England by seven wickets.

Unlike their 2003 success in South Africa, however, the Australians have not been pushed any harder than they were at Sir Vivian Richards Stadium as England sought their fourth consecutive victory over their Ashes rivals.

''There is still some improvement in this group, we haven't played our best cricket yet,'' said Ponting.

''We will be playing some very good cricket when we need to later on in the tournament.

''We went through 2003 undefeated and played some excellent cricket but we probably escaped a few more games through that tournament.

''I remember one against England where we got out of jail a little bit and there was another one against New Zealand (both at Port Elizabeth).

''We haven't had to do that yet. But to have a challenging, hard hit-out should make us better going forward.''

England have now lost three of their seven matches which will decide whether they go through to the semi-finals but Ponting refused to discount their chances in a head-to-head battle with South Africa and West Indies for the fourth semi spot.

''They will be as competitive as the other two sides,'' said Ponting.

''South Africa the other day didn't play the way I thought they would play against Bangladesh, I thought they would win that game pretty easily.

''I have thought right the way through that South Africa are probably the second-best side in the tournament.

''It is up to those three sides now to put their hands up and grab that last spot.

''It is going to be very competitive, there are some very good teams in this tournament, as everyone said at the start."

Injury to all-rounder Shane Watson is causing the Aussies their biggest headache and his replacement yesterday was Lancashire batsman Brad Hodge, with Michael Clarke and Andrew Symonds were called upon to bowl ten overs between them.

''We will have to look at conditions in other matches,'' said Ponting. ''We thought we would could get away with it with a low, slow wicket and both those guys had to bowl inside powerplays."