At 12.00pm (AEDT), the dollar was trading at $US0.6310/15, down from Friday's close of $US0.6455/60.
Since 07.00am AEDT, the unit has moved between a low of $US0.6300, reached just after 11.30am AEDT, and a high of $US0.6399.
The dollar opened at $US0.6365/71 at 0700 AEDT, its weakest start to the local session since February 1, when the unit began the trading day at $US0.6301/05.
The unit lost almost one US cent during offshore trading after a downward revision to US growth figures prompted safe-haven US dollar buying.
The preliminary estimate of US gross domestic product (GDP) showed the world's largest economy contracted at an annualised pace of 6.2 per cent in the December quarter, which was worse than the advanced estimate of a 3.8 per cent decline.
The dollar managed a mid-morning rally almost up to $US0.6400, but the move was not sustained.
The unit reacted negatively to Australian Bureau of Statistics data which showed company profits fell 6.5 per cent in the December quarter.
Over the same period, business inventories declined 1.9 per cent.
OzForex senior corporate dealer Euan McCreadie said the weak figures left the dollar vulnerable at the start of a busy week of economic data.
"It doesn't set a good tone,'' Mr McCreadie said.
"The Aussie looks fairly vulnerable as we start the week.''
Mr McCreadie said he expected the dollar to trade between $US0.6280 and $US0.6350 for the rest of the local session.
"Risk aversion is still there for the Aussie and the kiwi at the moment,'' Mr McCreadie said.
"The main benefactor of that has been the greenback over the course of the last couple of days.''
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