The kiwi is likely to be "slightly bullish" today ahead of the Fed decision scheduled for release at 6am New Zealand time tomorrow, Speizer said.
"If they remove the language, the US dollar will go back up, if they don't remove the language, it will probably stay down," Speizer said.
Early this morning, dairy product prices rose in Fonterra Cooperative Group's latest GlobalDairyTrade auction, inching higher from the lowest level since July 2012, as declines in butter milk powder and cheddar were offset by gains in rennet casein and skim milk powder.
That probably came as a relief to some, following recent sharp falls, although it wasn't the main reason for the kiwi's strength this morning, Bank of New Zealand markets strategist Kymberly Martin said in a note.
Today, New Zealand second quarter balance of payments data is scheduled for release at 10:45am.
The New Zealand dollar slipped to 90.12 Australian cents from 90.58 cents yesterday, was little changed at 50.35 British pence from 50.33 pence, advanced to 63.25 euro cents from 63.08 cents and gained to 87.83 yen from 87.53 yen.