The US Senate delayed until later Sunday a key test vote on a Democratic plan to raise the country's debt limit as signs of progress emerged in negotiations to strike a deal to avert a damaging default. With a Tuesday deadline looming to raise the government's $14.3 trillion borrowing limit, lawmakers are fighting against the clock to forge a bipartisan compromise agreement that can pass both the Democratic-controlled Senate and the House of Representatives, which Republicans lead. Negotiators more recently have been focusing on a possible $2.8 trillion debt limit increase tied to equal spending cuts, but the final number is still not set, an aide familiar with the talks told Reuters. But after a week of bitter partisan sparring that had brought the world's largest economy ever closer to default while the world watched incredulously, the atmosphere for a hoped-for eleventh-hour compromise appeared to improve. “There's certainly a more positive feeling about reaching an agreement this evening that I've felt in a long time,” Senator Richard Durbin, the No. 2 Democrat in the Senate, said. Earlier, Senate Republican leader Mitch McConnell and House Speaker John Boehner expressed confidence a bipartisan deal could be forged after their contacts Saturday with President Barack Obama and Vice President Jose Biden. As Tuesday's deadline drew nearer, the phone discussions between the Republican leaders and the White House seemed a positive step as the president had remained mostly sidelined from congressional discussions during the week. “I think we've got a chance of getting there,” McConnell said. Reid had said earlier on Saturday a deal was not close. Unless Congress raises the debt ceiling by Tuesday, the government would be barred from further borrowing after then, according to the US Treasury, and could quickly run out of money to pay all its bills. “Our country is not going to default for the first time in its history ...that's not going to happen,” McConnell said. A US default would plunge financial markets and economies around the globe into turmoil. The political gridlock has also put the US at risk of losing its top-notch Triple A credit rating. A downgrade could prompt global investor flight from US bonds and the dollar, raising borrowing costs for Americans when the economy remains fragile. ccording to an aide familiar with the ongoing talks, the negotiators were zeroing in on a plan for triggering broad, automatic spending reductions if an agreement on additional savings gets hung up in Congress later this year.