"Mr President, this is your moment," Mr Boehner said in a speech at the Capitol. "We're ready to lead, not as Democrats or Republicans, but as Americans."

For his part, Mr Obama contacted Mr Boehner and other congressional leaders to reopen negotiations before he had even left Chicago.

The Dow Jones industrial average lost 2.4 per cent over the day, in part because of fears over the fiscal cliff, and because Mr Obama's victory means new industry regulations will stay in place.

Unless an agreement between the parties is made by the end of the month, US$560 billion ($A537 billion) worth of tax and spending cuts will automatically kick in on January 1, though it is expected that if a permanent deal is not found the parties will agree to delay the impact.

The Congressional Budget Office estimates that should the measures go into effect, growth would drop by 4 per cent, forcing the nation back into recession, and 2 million jobs would be lost.

The measures were part of a compromise and made law when Congress was unable to come to a deal to resolve the debt-ceiling crisis.

They were deliberately designed to be so appalling to both parties (they include massive cuts to defence for Republicans, extensions to the Bush tax cuts for Democrats) that they would be motivated to come to a permanent solution.

Mr Boehner claimed both parties had won a mandate, because Republicans had retained control of the House of Representatives. He also again rejected tax hikes to help bring down the deficit and debt.

But he did open the door to increasing revenue by closing loopholes and reforming the tax code, thereby stimulating the economy.

"For purposes of forging a bipartisan agreement that begins to solve the problem, we're willing to accept new revenue, under the right conditions," he said.

This option had previously been rejected by Mitt Romney and congressional Republicans, most of whom are bound by an oath they have signed at the behest of anti-tax lobbyist Grover Norquist not to increase taxes in any way.

It is unclear how much money closing loopholes and reforming the tax code would raise. US debt is now more than $16 trillion.

Senate Majority Leader Harry Reid, a Democrat, said he was willing to negotiate, adding that the simplest way to avoid the cliff would be to allow tax cuts to expire for people earning more than $250,000 a year, as the President had proposed during the campaign.

Mr Boehner appeared to reject that idea.

"The American people this week didn't give us a mandate to do the 'simple' thing," he said. "They elected us to lead."

Mr Obama did not address the issue on Wednesday, although The New York Times quoted a senior administration official as saying: "This election tells us a lot about the political wisdom of defending tax cuts for the wealthy at the expense of everything else."

Both Mr Obama and Mr Boehner attempted to come to a "grand bargain" over the issue during the last term, and both were bruised by the experience, each claiming the other had sabotaged the negotiations.

Mr Obama also appeared to mention it in his victory speech, saying "tonight you voted for action, not politics as usual. You elected us to focus on your jobs, not ours. And in the coming weeks and months, I am looking forward to reaching out and working with leaders of both parties to meet the challenges we can only solve together.

"Reducing our deficit. Reforming our tax code. Fixing our immigration system. Freeing ourselves from foreign oil. We've got more work to do."