WASHINGTON (Reuters) - Deep beneath the Capitol is a red-carpeted room that recently reverberated to the sound of Democrats and Republicans singing together, and then to their angry exchanges over how to fix the U.S. budget.
Welcome to Congress's "super committee" room.
This is where a dozen lawmakers lock themselves away to try to strike a deal that, if reached, could prove a turning point in one of the United States' biggest challenges: shrinking its huge budget deficits and containing its soaring debt burden.
On a dozen occasions so far since early September, the committee's six senators and six members of the House of Representatives pulled up a dozen yellow chairs to four wooden tables pushed into a square and commenced haggling over spending and taxes.
There is no assigned seating in the bare 30-by-30 foot Room 200 in the Capitol's visitors' center, two floors underground.
Instead the six Republicans and six Democrats routinely change places as they try new ways to find a deal by November 23 to cut the deficit by at least $1.2 trillion over 10 years.
The swings between comity and acrimony do not yet signal whether a deal can be done by the deadline.
Failure could stoke fears among investors around the world that the U.S. political system is incapable of coming to grips with the country's huge debt.
All of this is happening at a time when Congress's approval rating among Americans has sunk to an all-time low of less than 10 percent, largely because of partisan gridlock.
"At this point, the most serious adult conversations going in Congress are at the super committee," a senior aide said.
"Members are driven by a sense that this is a very precarious time in U.S. history that beckons a solution," the aide said. "But at the same time, members wrestle with political loyalties that they can't divorce themselves from."
Democrats are pushing to cut the deficit by up to $3 trillion over 10 years, much higher than the super committee's target, with a mix of spending cuts and new tax revenues. But Republicans deeply oppose raising taxes, warning of job losses and damage to an already fragile economic recovery.
Across the divide, friendships have blossomed in Room 200. Democratic Senator John Kerry and Republican Senator Rob Portman have started biking together in the morning.
Kerry has emerged as a leader of an informal, bipartisan group of six lawmakers within the super committee, the biggest of a number of sub-groups seeking to narrow differences.
He recently invited a few of his group of six, including Portman, to his home for dinner, congressional aides say.
Senator Patty Murray, the panel's Democratic co-chair, and Jeb Hensarling, the committee's Republican co-chair, have a solid working relationship, according to aides who asked not to be identified because of the panel's secrecy policy.
Yet some opposing positions have seemed to harden, like those between Democratic Senator Max Baucus, who like other Democrats wants all budget options on the table, and Republican Senator Jon Kyl, who fiercely opposes any new defense cuts.
Tensions rose on October 25 when the Democrats unveiled their $3 trillion plan. As Baucus made the pitch, Republicans on the panel, led by Kyl, interrupted with blunt objections. "We haven't signed off on any revenues, and we certainly aren't doing anything that high," an aide quoted Kyl as saying.
At that point, as is the case whenever the talks get tough, all staff were ordered out, leaving only committee members to cool off and try to move on.
The veil of silence holds outside the room, too. Reporters stalking the super committee members have largely come up empty-handed. Many of the lawmakers emerge from the talks holding up their hands to signal they have nothing to say.
To fuel the debates, some of which have lasted much of the day, a pair of metal coffee makers and a red plastic container of Folgers Classic Roast sit atop a small table in a corner of the room.
"Coffee is the drink of choice, more so than soda or bottled water. It helps keep them going," an aide said.
On the other side of the room, a tray is laden with nibbles including cookies, raisins, trail mix, nuts and Doritos.
Generally members don't munch much during their sessions, though on one day Kerry treated colleagues to cupcakes. Another time, Kyl brought sandwiches from a popular lunch chain.
In October, members set aside their differences for long enough to sing "Happy Birthday" to the panel's Democratic co-chair, Murray.
Aides say talks have generally been cordial, at least in part because it features none of the lawmakers who are considered to be Congress's leading hot-heads.
Republican Senator Pat Toomey has a reputation for being mild mannered. He is a favorite of the conservative Tea Party movement which is pushing hard for spending cuts and no tax increases. But Toomey has signaled that he wants a deal.
Kerry, the Democratic Party's failed 2004 presidential nominee, has emerged as of the panel's most talkative members, at times irritating some, but drawing respect from both sides for his efforts.
Portman, a budget director in the administration of Republican President George W. Bush, has been among the chief advocates for a reform of America's complex, loophole-riddled tax system that could generate more revenue without necessarily raising tax rates.
Some members of the six-strong sub-group led by Kerry recently had dinner in a Chinese restaurant on Capitol Hill, shortly after Republicans privately presented their $2.2 trillion proposal based mainly on cuts to social programs.
Committee Democrats rejected the Republican idea.
If the committee fails to reach a deal before its deadline, $1.2 trillion in automatic spending cuts are scheduled to kick in from 2013, although lawmakers could yet undo them. Such cuts could trigger an outcry as they would bite into each party's sacred cows: defense spending for Republicans and social welfare programs for Democrats.
Less than three weeks before the deadline, few who follow the discussions venture to guess the prospects for success.
"We aren't going to know if we're going to get a deal until seven days or less before the deadline," said a senior aide. "That's when things will get really serious."
Additional reporting by Tim Reid, Richard Cowan and Donna Smith; Editing by Vicki Allen