The Australian currency finished stronger after it held on to most of its overnight gains, despite a lower than expected trade surplus jolting investor appetite for the unit.

At the local close, the currency was trading at $US0.9073, up from Wednesday's close of $US0.9011.

The Aussie started the domestic session at $US0.9113, its strongest opening to a local trading day since August 11 at $US0.9135.

The Australian dollar added 1 US cent overnight after data showed the US manufacturing sector increased in August for the 13th straight month, a cause for optimism that the American economy will recover without delay.

CMC markets foreign exchange dealer Tim Waterer said, ''we've seen it retrace those overnight highs.''

''That's not unusual given the strong run up it had overnight.''

The Aussie, however, dipped back from its highs during the morning and after the announcement of Australian trade figures showing a $1.888 billion surplus in July, from a downwardly revised surplus of $3.438 billion in June.

Economists said there was a sharp drop off in ore and coal exports to China, which closed 40 per cent of its steel industry for maintenance in July, that contributed to the worse than expected trade report.

Mr Waterer said investors would not make any big currency moves until the release of key US employment data during the offshore session.

The US Department of Labour on Thursday night is scheduled to publish its initial jobless claims report for the week ending August 28.

Analysts forecast jobless claims to increase to 480,000 from 473,000 the week before.

Lower than expected figures could insight risk appetite and lift the Australian dollar, said Mr Waterer.

''We're within stalking distance of $US0.91.''