The US Conference Board's consumer confidence index fell to 122.1 this month from a revised 128.6 in November, when it reached a 17-month high, helping drive the US dollar index to its lowest level in more than three weeks.
The CRB Index of 19 commonly traded commodities rose 0.5 per cent to its highest in a month as crude oil and copper gained, helping lift currencies of producers such as Canada and Australia.
"US consumer confidence was less than expected and that's led to a broad US dollar selloff," said Stuart Ive, a senior dealer at OMF.
"When the US dollar falls, commodity currencies tend to outperform. Oil and copper are supporting the Aussie and the Canadian dollar."
Ive said during the holiday season trading flows in foreign exchange markets are about 20 per cent below normal levels.
There has been a continuation of softness in the greenback "but that could change dramatically in January as the potential of (US) tax reforms starts taking a grip," he said.
The kiwi fell to 90.87 Australian cents from 91.03 cents late yesterday. It rose to 80.02 yen from 79.78 yen and rose to 4.6331 yuan from 4.6180 yuan. It was little changed at 59.39 euro cents from 59.38 cents and rose to 52.73 British pence from 52.67 pence.