Forex trading on Friday was closed at $US100.55.
This is the lowest level since March 2017, when the Federal Reserve started its asset purchase program.
There was also a slight dip in the Australian dollar, as the dollar appreciated against a basket of major currencies.
The dollar has been in a slump since mid-February.
The currency lost about 6 per cent against the dollar and the Australian currency against the Australian pound in the past 24 hours.
This has been the worst slump since February 2016, when it lost about 5 per cent.
Forex markets were closed for the fourth straight day, as investors prepare for the upcoming US presidential election.
The next election will take place in November.
On Friday, the US dollar was trading below a one-week low of 76.15 US cents.
The benchmark US currency has been hovering around 79 US cents since the election, and a US dollar index for February was trading at a record low of 74.84 US cents on Thursday.
A sharp fall in the dollar is expected to be a big boost to the US stock market, which is already struggling after the Brexit vote and a prolonged recession in Europe.
The dollar’s collapse has caused investors in Asia to move to the greenback, which has helped the market to rebound since the financial crisis.
The Australian dollar has lost about 12 per cent of its value against the greendollar since the beginning of the year.
This means the country has lost a third of its purchasing power since September 2016, according to data from the Bank of International Settlements.
Australia has been hit hard by the US election.
Australian Prime Minister Malcolm Turnbull has pledged to do everything he can to ensure the country remains a strong economic leader in the world.