At 12.00pm AEDT, the Australian dollar was trading at $US0.7002/06, up from Wednesday's close of $US0.6876/78.
During the morning, the unit moved between a low of $US0.6977 and a high of $US0.7008.
The Australian dollar had opened firmer on improved risk appetite, after US equity markets posted strong gains on Wednesday.
Encouraging US home sales data added to positive market sentiment, lifting the local unit to $US0.6993/99 at the start of the local trading day at 7.00am AEDT.
Later, the Australian dollar reacted positively to an improvement in the nation's trade balance in February.
The balance of goods and services was a surplus of $2.109 billion, seasonally adjusted, in February, from a downwardly revised $926 million surplus in January, according to figures from the Australian Bureau of Statistics (ABS).
The result was well above financial market forecasts of a $700 million surplus.
During the month, exports rose by 4.0 per cent in adjusted terms, while imports were down 1.0 per cent.
ANZ Banking Group head of foreign exchange Amy Auster said the widening trade surplus did result in some Australian dollar buying, but there was little follow through.
"It's obviously a very positive trade balance but the data behind it is obviously more of a mixed bag," Ms Auster said.
"Imports were weaker than expected and that's not a good sign for consumption or interest rates in Australia."
The Australian dollar was trading at $US0.6977 just before the data were released at 11.30am AEDT, and reached its intraday high of $US0.7008 shortly afterwards.
Ms Auster said the Australian dollar was expected to trade quietly ahead of the ECB board meeting and interest rate decision, due during Thursday night's (AEDT) offshore session.
"That's the main thing everybody is going to be looking for," Ms Auster said.
"We've probably seen the high for today I would say and we'll just drift probably lower over the session."
Financial markets have forecast the ECB to lower is key lending rate by 50 basis points to one per cent.
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