The kiwi's "been weak for the last two or three days. It looks like it got sold on momentum once it broke through the November low of 0.6975 (US cents)," with the move exacerbated by thin pre-Christmas trading, said ASB head of FX institutional sales New Zealand Tim Kelleher.
Looking ahead, Kelleher said if it breaks below 68.50 US cents "we will be at 65 pretty quickly."
He said the overnight GlobalDairyTrade auction is unlikely to have much impact as the market is already expecting prices to dip, partly on increased volumes on offer.
The kiwi held up fairly well against the Australian dollar on the day, which was harder hit by a fall in other Asian currencies such as the Malaysian Ringgit, he said.
The local currency traded at A95.45c from A95.5c late on Monday. It slipped to 4.8166 yuan from 4.8182 yuan and was at 81.25 yen from 81.24 yen. It traded at 66.54 euro cents from 66.66 cents and was at 55.85 British pence versus 55.91p.
New Zealand's two-year swap rate was unchanged at 2.38 per cent, and 10-year swaps were down two basis points at 3.55 per cent.