PRIME Minister Julia Gillard said Australia had worked closely with President Obama and his administration over the past four years, adding ''I look forward to continuing this friendship''.
The government is relieved at the status quo result as it heads into its own election year; a Romney presidency could have created new international uncertainty.
Ms Gillard said that US leadership ''remains vital to meeting global challenges: international financial stability and global economic growth, peace and security, and the impacts of our changing climate''. She said the two countries would work together on the United Nations Security Council in 2013-14 during Australia's term as a non-permanent member.
''Australia and the United States are unique partners,'' she said.
In a briefer congratulatory statement, Tony Abbott said: ''The United States is Australia's largest and most important ally and Australia can look forward to a continuation of the best possible relations.''
Foreign Minister Bob Carr predicted that in his second term Mr Obama would try to revive international talks on climate change and that he would "focus tightly" on Iran and non-proliferation.
He told ABC Radio that Mr Obama might also look to push for a "two-state solution" in the Middle East.
Senator Carr also expressed hope that the US would find a solution to the so-called "fiscal cliff" looming at the end of the year.
"[We've] got to hope that there are enough people on both sides of American politics to reach across the aisles of the Senate and the House of Representatives to do a deal ... to see that America can curb that deficit."
Senator Carr congratulated Mr Obama on his election victory as well as the American people for their participation in the vote.
"There's nothing like a drawn out, bruising, American election contest," he said. "It's the greatest show on earth and it's a celebration of democracy."
Coalition foreign affairs spokeswoman Julie Bishop also congratulated Mr Obama before pointing to challenges in Europe, tensions between China and Japan and the US's domestic economic woes as immediate concerns.
"There are still these challenges in the United States itself that must be addressed and that will be the first issue that the President will have to address to ensure that fiscal cliff is avoided," Ms Bishop told Sky News on Wednesday.
"It is the largest economy in the world. The United States, of course, is our third-largest trading partner and our number one military ally. So stability and prosperity in the United States is exceedingly important, not only for Australia but for the globe generally."