The U.S. Senate will hold a rare Sunday session as US politicians grapple with how to reopen the shuttered government and avoid a potentially calamitous failure to pay the country’s debt obligations.

The U.S. Senate will hold a rare Sunday session as US politicians grapple with how to reopen the shuttered government and avoid a potentially calamitous failure to pay the country's debt obligations.

With Republicans in the House of Representatives blaming President Barack Obama for the collapse of talks on extending US borrowing authority, the Senate's Republican and Democratic leaders scrambled to piece together a bipartisan exit strategy.

The top senators showed an intensifying desire to end the two-week government shutdown and ease the threat of default with just three working days next week before the US Treasury's October 17 deadline for raising the debt ceiling.

Democratic Senate Majority Leader Harry Reid, Obama's top wingman in Congress, said he held "extremely cordial but very preliminary" talks Saturday with top Republican Senator Mitch McConnell.

McConnell suggested a bipartisan offer spearheaded by moderate Republican Senator Susan Collins as a workable template, but Reid rejected it.

The measure would extend borrowing authority into 2014 and fund the government for six months, but it would also repeal a medical device tax introduced under Obama's health care law.

Democratic leaders were most concerned, however, with the proposal to keep the existing automatic spending cuts, a move that would put agency spending at $70 billion below what Democrats have proposed for fiscal 2014.

With negotiations with the Republican-controlled House of Representatives in tatters, Obama called a snap meeting at the White House with the Senate's Democratic leadership to regroup.

Obama on Saturday made clear that he wanted a long-term deal, rejecting a proposal floated by House Speaker John Boehner suggesting a six-week extension to US borrowing authority.

House Republicans have argued for any budget deal to include concessions on funding Obama's health care reforms, while Senate Republicans are more willing to reopen government without such conditions.

The government, shuttered since October 1, would be fully reopened, possibly on an interim basis.

Both sides would also commit to work toward an elusive deal to tackle the deficit, rein in spending and possibly reform social programs and some aspects of the tax code.

But, perhaps sensing that it now has the upper hand in the fight, the White House has rejected the idea of extending the borrowing authority by just six-weeks.