US Republican presidential candidate Mitt Romney has accused US President Barack Obama of standing by while a looming budgetary calamity unfolds in Washington.

Mr Romney leaped into the debate over the "fiscal cliff," the potential for an end-of-the-year uproar when some $109bn in across-the-board spending cuts kick in unless Mr Obama and Congress reach a deficit-reduction deal to avert them.

Bush-era tax cuts also expire at year's end.

The Washington debate mirrors the campaign battle between Mr Obama and Mr Romney.

Democrats want to make up the shortfall by increasing taxes on wealthy Americans while Republicans favour spending cuts.

"Political gridlock threatens to plunge us back into recession, but instead of seeking bipartisan solutions, President Obama is passively allowing us to go over a fiscal cliff," Mr Romney said in his weekly podcast.

The White House said in releasing a breakdown of the cuts on Friday that it was congressional Republicans who are standing in the way of a deal because they refuse to accept a more balanced approach.

The White House and Congress, Democrats and Republicans, including Mr Romney's vice presidential running mate, Paul Ryan, agreed on the automatic cuts under an August 2011 deal.

Mr Romney, who has vowed to build up the US military if elected on 6 November, has singled out for criticism the $54bn in defence cuts that would kick in at year's end. He says this is no time to shrink the Pentagon's budget.

"What kind of commander-in-chief forces Americans to choose between massive tax hikes that will undermine the economy and massive cuts to our military that will undermine national security?" said Romney spokeswoman Andrea Saul.

Mr Romney is ending a rough week during which he fell behind Mr Obama in the polls and came under criticism from Democrats and some Republicans for making a campaign issue of the deaths of four Americans killed by Muslim protesters at the US diplomatic mission in Benghazi, Libya.

The candidate took a day off from the campaign trail yesterday. He spent part of the afternoon watching one of his grandson's soccer games.