With only four days to go before the US government falls over the 'fiscal cliff' of tax hikes and budget cuts, GOP aides in the House of Representatives told NBC News that House members would reconvene Sunday -- two days before the deadline -- to resume talks.
Earlier, the Senate returned Thursday with Majority Leader Harry Reid expressing doubt that a deal can be reached to avoid the automatic confluence of higher taxes and deep spending cuts.
"it looks like that's where we're headed," Reid said of the "fiscal cliff." He accused Speaker John Boehner of running a "dictatorship" by "not allowing the vast majority of the House of Representatives to get what they want."
Stock prices dropped after Reid spoke. The Dow dropped into negative terrirtory for December and fell below 13,000 for the first time since Dec. 5. (Read More: Stocks Skid Amid 'Cliff' Fears, Data)
President Barack Obama arrived back in Washington on Thursday, cutting short his Hawaii vacation to face the showdown in the nation's capital with even a stopgap solution now in doubt. Before leaving, he made phone calls to Reid, Boehner, Senate Republican leader Mitch McConnell and House Democratic leader Nancy Pelosi, the White House said.
On the Senate floor, Reid challenged Boehner to call the House back into session.
"They've done nothing," Reid said of the GOP-controlled House. "The speaker has just a few days left to change his mind," Reid said, but added: "I don't know time wise how it will happen."
Reid also took to Twitter, tweeting: "The way to avoid the 'fiscal cliff' has been in the face of GOP leaders for months - taking up the Senate-passed mid.-class tax cut bill."
Boehner spokesman Brendan Buck retorted: "Harry Reid should talk less and legislate more if he wants to avert the fiscal cliff. The House has already passed legislation to do so."
The House has passed a Republican plan to avert the fiscal cliff, and the Senate has passed a Democratic version. Their deficit-reduction projections differ by hundreds of billions of dollars over 10 years.
Republican Sen. Scott Brown created a brief stir Thursday by saying on Facebook that Obama had presented a new proposal to the Senate GOP leadership, but the White House told NBC News that no new plan had been offered.
Adding to the mix of developments pushing toward a "fiscal cliff," Treasury Secretary Timothy Geithner informed Congress on Wednesday that the government was on track to hit its borrowing limit on Monday and that he would take "extraordinary measures as authorized by law" to postpone a government default. (Read More: Geithner Warns US to Hit Debt Ceiling Monday)
Still, he added, uncertainty over the outcome of negotiations over taxes and spending made it difficult to determine how much time those measures would buy.
In recent days, Obama's aides have been consulting with Reid's office, but Republicans have not been part of the discussions, suggesting much still needs to be done if a deal, even a small one, were to be struck and passed through Congress by Monday.
At stake are current tax rates that expire on Dec. 31 and revert to the higher rates in place during the administration of President Bill Clinton. All in all, that means $536 billion in tax increases that would touching nearly all Americans. (Read More: Here's How a 'Cliff' Dive Will Affect Your Taxes) Moreover, the military and other federal departments would have to cut $110 billion in spending.
But while economists have warned about the economic impact of tax hikes and spending cuts of that magnitude, both sides appear to be proceeding as if they have more than just four days left. Indeed, Congress could still act in January in time to retroactively counter the effect on most taxpayers and government agencies, but chances for a large deficit reduction package would likely be put off. (Read More: Over the 'Cliff': What Kind of Landing?)
House Republican leaders on Wednesday said they remain ready to negotiate, but urged the Senate to consider or amend a House-passed bill that extends all existing tax rates. In a statement, the leaders said the House would consider whatever the Senate passed. "But the Senate first must act," they said.
Aides said any decision to bring House members back to Washington would be driven by what the Senate does.
Reid's office responded shortly after, insisting that the House act on Senate legislation passed in July that would raise tax rates only on incomes above $200,000 for individuals and $250,000 for couples.
Meanwhile, Obama has been pushing for a variant of that Senate bill that would include an extension of jobless aid and some surgical spending reductions to prevent the steeper and broader spending cuts from kicking in. (Read More: Stop-Gap Fix Most Likely Outcome of US Fiscal Talks)
For the Senate to act, it would require a commitment from Senate Republican Leader Mitch McConnell not to demand a 60-vote margin to consider the legislation on the Senate floor. McConnell's office says it's too early to make such an assessment because Obama's plan is unclear on whether extended benefits for the unemployed would be paid for with cuts in other programs or on how it would deal with an expiring estate tax, among other issues.
What's more, House Speaker John Boehner would have to let the bill get to the House floor for a vote. Given the calendar, chances of accomplishing that by Dec. 31 were becoming a long shot.
Amid the standoff, Geithner advised Congress on Wednesday that the administration will begin taking action to prevent the government from hitting its borrowing limit. In a letter to congressional leaders, Geithner said accounting measures could save approximately $200 billion.
That could keep the government from reaching the debt limit for about two months. But if Congress and the White House don't agree on how to avoid the "fiscal cliff," he said, the amount of time before the government hits its borrowing limit is more uncertain.
"If left unresolved, the expiring tax provisions and automatic spending cuts, as well as the attendant delays in filing of tax returns, would have the effect of adding some additional time to the duration of the extraordinary measures," he wrote.
Whenever the debt ceiling hits, however, it is likely to set up yet another deadline for one more budget fight between the White House and congressional Republicans.
Initially, clearing the way for a higher debt ceiling was supposed to be part of a large deal aimed at reducing deficits by more than $2 trillion over 10 years with a mix of tax increases and spending cuts, including reductions in health programs like Medicare. But chances for that bargain fizzled last week when conservatives sank Boehner's legislation to only let tax increases affect taxpayers with earnings of $1 million or more. (Read More: Boehner Abruptly Scraps 'Plan B' Vote)
Obama and his aides have said they would refuse to let Republicans leverage spending cuts in return for raising the debt ceiling. But Republicans say the threat of voting against an increase in the limit is one of the best ways to win deficit reduction measures.
Another potential showdown is pending. A renewed clash over spending could come in late March; spending authority for much of the government expires on March 27.
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