During the morning, the dollar moved between a low of $US0.7003 and a high of $US0.7079.
It opened stronger at $US0.7006/11 at 07.00am AEDT, the first time since October 21 it has started the local trading session above $US0.7000.
The dollar continued to appreciate against the US dollar, but mostly traded sideways against other currencies such as the Japanese yen, euro and New Zealand dollar.
Commonwealth Bank of Australia currency strategist Joseph Capurso said the higher Australian dollar is a sign of renewed weakness in the US dollar.
"On the cross rates, the Aussie dollar isn't doing that well, so that suggests that it's mainly about a weakening US dollar as people get more concerned about rising debt levels and the like in America,'' Mr Capurso said.
"It's not broad based at all.
"It's probably not so much a story about us as about America.''
Mr Capurso expected the Australian dollar to move above $US0.7100 during afternoon trading, but said its stay was likely to be brief.
"It looks like this momentum could continue for a little while longer,'' Mr Capurso said.
"But I have to say we can certainly see plenty of downside risks to the Aussie.
"The economic outlook for the world is certainly getting worse, not better, and that is a very big influence in the Aussie dollar.''
Falling oil prices, despite the Organisation of Petroleum Exporting Countries' (OPEC) decision to cut oil production by 2.2 billion barrels a day, would also eventually weigh on the Australian dollar, Mr Capurso said.
Separately, the Reserve Bank of Australia said it had bought $134 million worth of Australian dollars in November, compared with $3.15 billion the previous month.
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