We haven't got into second gear yet, says Duminy ahead of World Cup

South Africa is poised to take over the top ranking in international limited-overs cricket and allrounder J.P. Duminy says the Proteas are "comfortable" with the way they are tracking toward next year's World Cup.

Duminy scored 58 not out in South Africa's emphatic six-wicket win over New Zealand to open a three-match ODI series on Tuesday and issued a tacit warning to Cup rivals that they are currently playing well below their best.

If South Africa sweeps the series, which continues with matches on Friday and Monday, it will take over the top ODI ranking from Australia.

Duminy says "if we're honest we were probably 65-70 per cent" in the opening match and "it's good to be able to win games like that."