By Emily Goodin - 12/30/12 11:00 PM EST
Senators have been warned they may be spending New Year's Eve together -- working on a last-minute deal to avoid the "fiscal cliff."
"We've all been told not to make plans," Sen. Claire McCaskill (D-Mo.) told reporters in the Capital on Sunday evening. "We're all going to be here through tomorrow night, the first, the second, the third and so-on."
Both sides emerged from their meetings without news of a deal that would stave off tax raises and spending cuts set to go into effect on Jan. 1.
Most of the lawmakers looked pessimistic as they came out of the conference rooms to find hordes of reporters waiting on them.
Sen. Joe Lieberman (I-Conn.) said "I'd be shocked" if a deal was done on Sunday.
Sen. Barbara Mikulski (D-Md.) described the mood of the Democrats' meeting as "grim" despite the smatter of applause that rang out at different points.
And retiring Sen. Olympia Snowe (R-Maine), who is celebrating her last week in the upper chamber, had harsh words for her colleagues. She described the situation as "self-imposed" and a "failure of historic proportions."
But some senators tried to keep the mood light-hearted.
"I had a nice flight back from Vermont this afternoon -- gritting my teeth the whole way," joked Sen. Patrick Leahy (D-Vt.).
The upper chamber has been back in Washington since Wednesday while the House returned Sunday. Negotiations between the two sides remain ongoing.
McCaskill, asked if she was more optimistic now than she had been in this morning, responded: "I wouldn't say that."