At 12.00pm (AEDT), the dollar was trading at $US0.6422/26, up from Friday's close of $US0.6384/88.
During the morning, the unit moved between a low of $US0.6417, reached less than an hour after the local session opened, and high of $US0.6473.
The dollar advanced during Friday New York trading session, as investors took advantage of a recent appreciation of the US dollar to exit long positions on the American currency.
The unit opened at 07.00am AEDT at $US0.6436/45 and climbed to its intra-day high of $US0.6473 at about 10.30pm AEDT.
The move was not sustained, however, with the dollar falling about half a US cent as equity markets started the week on a negative note.
CMC Markets FX dealer Tim Waterer said weak equity markets dragged the dollar lower.
"It seems to be drifting lower due to the weakness in the Asian equity markets so far this morning,'' Mr Waterer said.
"Some of that negative sentiment seems to be flowing through to the Aussie dollar.''
At 12.00pm AEDT, the benchmark S&P/ASX200 index was down 2.48 per cent, while the broader All Ordinaries index was 2.36 per cent lower.
Bourses in Japan, Korea and New Zealand were also in the red.
Mr Waterer said some of the US dollar selling seen during the weekend offshore session had not followed through to this morning's trade.
"The US dollar is still remaining reasonably well bid, given the current economic backdrop,'' Mr Waterer said.
Mr Waterer said he expected the Australian dollar to trade between $US0.6400 and $US0.6500 during the rest of the local session.
"It's still finding support above 64 US cents, but basically it's just trading sideways at the moment,'' Mr Waterer said.
"That underlying US dollar strength is I guess making it a little bit difficult for the Aussie dollar to make any sort of headway above that $US0.6500 level at the moment.''
Large banks take beating on Wall Street
Dollar up at noon
Dollar falls to fresh low
