An eye-catching all-round performance by Mitchell Marsh carried Australia to a 62-run victory over South Africa on Tuesday to secure their place in the triangular series final.

Marsh struck a brutal 86 not out from 51 balls to boost the Australian total to 282 for seven, and then took two key wickets as South Africa were bowled out for 220 in 44 overs.

Faf du Plessis' brilliant 126 went in vain as none of his team-mates crossed 25, with Mitchell Johnson, Glenn Maxwell and Kane Richardson joining Marsh with two wickets apiece.

Victory secured Australia's participation in Saturday's final, where they should meet South Africa again.

The Proteas would need to be heavily beaten by Zimbabwe in Thursday's final round robin game to miss out on qualifying.