Kane Williamson's classy century gave New Zealand a four-wicket win over South Africa to top the standings and all-but end the Proteas' involvement.
South Africa 241-6 (49 overs): Van der Dussen 67*, Amla 55
New Zealand 245-6 (48.3 overs): Williamson 106*, De Grandhomme 60
New Zealand won by four wickets
Match Report
New Zealand went top of the World Cup table as a thrilling four-wicket win at Edgbaston effectively ended South Africa's interest in the tournament.
Chasing a modest 241 for victory in a 49-over contest, New Zealand were in trouble at 80 for four after opener Martin Guptill had been dismissed in freak fashion.
But Kane Williamson played a true captain's innings, making an unbeaten 106 from 138 balls, and crucial support from Colin De Grandhomme saw the Black Caps home with three balls to spare as they retained their unbeaten record.
It was a classy performance from Williamson, refusing to panic when wickets were lost around him, while De Grandhomme bludgeoned boundaries at the right time.
But how South Africa will curse lost opportunities. David Miller, having just been inches from catching Williamson off Imran Tahir, was unable to hold on to a difficult one-handed chance from the spinner when De Grandhomme was on 22.
Williamson should also have been run out on 77, but he went on to complete a 12th ODI hundred - levelling the scores with a six before striking the winning four off Andile Phehlukwayo.
South Africa skipper Faf Du Plessis had declared his side could afford no more slip-ups after taking only three points from their opening five games.