US senators have expressed hope that a bipartisan deal could emerge on Tuesday to end Washington's fiscal crisis that may lead US to default on its debt.
This comes even as Republicans in the House of Representatives said on Tuesday that they were working on a separate plan that included measures that would affect President Barack Obama's healthcare reforms, which have been at the heart of the crisis.
But the White House dismissed the the Republican proposals, calling it a partisan attempt to appease a small group of Tea Party conservatives.
White House spokesman Amy Brundage said Obama has vowed repeatedly that lawmakers "don't get to demand ransom for fulfilling their basic responsibilities to pass a budget and pay the nation's bills".
Brundage said Democrats and Republicans in the Senate have been working in a good-faith effort to end the fiscal stalemate and "it's time for the House to do the same".
The Senate Majority Leader, Harry Reid, said he was confident that Senate Democrats and Republicans can reach a comprehensive fiscal agreement this week to avoid the default.
"There are productive negotiations going on with the Republican leader. I'm confident we'll be able to reach a comprehensive agreement this week in time to avert a catastrophic default on the nation's bills," Reid said on the Senate floor.
Even if Democrats and Republicans agree, it could be Wednesday before the US Senate signs off on a plan, Senators said, close to a Thursday deadline when the Obama administration says it will reach its borrowing limit and risk default.
The Obama administration says it will be unable to pay all of its bills if Congress does not raise the $16.7 trillion debt limit by then.
"I think we'll get an agreement today in the Senate," Arkansas Democrat Mark Pryor told US news network, CNN.
"I'm not saying we can pass it today because there's logistics about drafting and getting it to the floor and the procedural things we'll have to do ... but my guess is we'll pass something in the Senate tomorrow."
Still at odds
Congressional sources said that the two sides in the Senate were still at odds over Democrats' demand for a delay in an insurance fee that is part of the new healthcare reforms, which are known widely as Obamacare.
The federal government has been in partial shutdown since October 1 when Congress missed the deadline for funding it.
Conservative Republicans prompted the crisis, which has rattled global markets, by demanding major changes to the healthcare reforms as a condition of passing a government spending bill and raising the debt ceiling.
The tentative Senate agreement does not defund or delay the healthcare reforms, but some Senate Republicans are seeking minor changes such as tougher income verification for those seeking insurance subsidies under the law and delay to a so-called reinsurance fee.
Amy Klobuchar, a Minnesota Democrat who is part of a bipartisan group of senators trying to forge a compromise, said an agreement would buy time for a more thoughtful process to settle longer-term budget issues.
The deal would reopen the federal government, pay US bills and allow the parties to commit to further negotiate, she told MSNBC's "Morning Joe" programme. "Those are the bright spots."
Numerous polls show Republicans have taken a hit in opinion polls since the standoff began.