None of it was a promising prelude to negotiations scheduled to resume at the White House on Thursday afternoon, less than three weeks before an Aug. 2 deadline for increasing the government's borrowing authority. Thursday's talks were to focus on the touchy questions of how to cut spending on Medicare and Medicaid, and raising more tax revenue.

Behind the scenes, meanwhile, legislators and White House officials continued to work on a backup plan offered by McConnell to avoid government default.

Obama is demanding that budget negotiators find common ground by week's end, as the financial world watches with growing jitters.

"No one can tell me with certainty that a U.S. default wouldn't cause catastrophe and wouldn't severely damage the U.S. or global economy," Jamie Dimon, CEO of JPMorgan Chase & Co., told reporters Thursday. "And it would be irresponsible to take that chance."

Already, Moody's Investors Service is reviewing the government's credit rating, saying there is a small but rising risk that the government will default on its debt. If Moody's were to lower the rating, the consequences would ripple through the economy, pushing up rates for mortgages, car loans and other debts. A Chinese rating agency, Dagong Global Credit Rating Co., also warned of a possible downgrade.

Reid sketched the potential consequences of default in dire terms, saying Social Security checks, veterans benefits and paychecks for troops would stop. "Millions of Americans could lose their jobs," he added.

A Reid spokesman later clarified that Social Security benefits "could" stop, as Obama previously had warned, but it wouldn't be a certainty.

Republicans have called such statements scare tactics.

In the cauldron of the White House Cabinet Room, Obama and top lawmakers bargained for nearly two hours Wednesday. Obama curtly ended the session when Cantor, R-Va., urged him to accept a short, monthslong increase in debt instead of one that would last through next year's presidential election.

"Enough is enough. … I'll see you all tomorrow," Obama said, rising from the negotiating table and leaving the room, according to several officials familiar with the session.

Reid said that while other Republican leaders were willing to negotiate in good faith, Cantor "has shown he shouldn't even be at the table."

The United States hit its current $14.3 trillion debt ceiling in May and the Obama administration says the government will default on its obligations if the debt limit is not increased by Aug. 2. For a new debt ceiling to last to the end of 2012 would require raising it by about $2.4 trillion.

Republicans, in control of the House of Representatives in part because of the support of tea party activists, say they will not vote to raise the limit if Obama doesn't agree to at least an equal amount of deficit reductions over 10 years.

Obama and the top eight House and Senate leaders met for the fourth time in as many days Wednesday, and, despite the tense ending, agreed to meet again Thursday.

A congressional aide said the White House discussed with lawmakers the possibility of moving talks this weekend to the presidential retreat at Camp David in Maryland. But a spokesman for House Speaker John Boehner said the Ohio Republican told the White House he saw no need for that. And Obama aides later said they planned to continue holding meetings at the White House for the next few days.

Despite McConnell's assertions that the debt problem belongs to Obama, fresh polling from Quinnipiac University suggested voters would be more apt to hold Republicans responsible than Obama, by 48 percent to 34 percent, if the debt limit is not raised. The same survey showed voters were about evenly split on whether they're more concerned about raising the limit and increasing government debt, or seeing the government go into default and damaging the economy.

"The American people aren't very happy about their leaders, but President Barack Obama is viewed as the best of the worst, especially when it comes to the economy," said Peter Brown, assistant director of Quinnipiac's Polling Institute.

That helps explain why McConnell put forward a plan that would give Obama new powers to overcome Republican opposition to raising the debt ceiling.

The proposal would place the burden on Obama to win debt ceiling increases up to three times, provided he was able to override congressional vetoes — a threshold Obama could manage to overcome even without a single Republican vote and without massive spending cuts. Conservatives promptly criticized the plan for giving up the leverage to reduce deficits. But the plan raised the prospect of combining it with some of the spending cuts already identified by the White House in order to win support from conservatives in the House.

In an interview with radio talk-show host Laura Ingraham, McConnell described his plan in stark political terms, warning fellow conservatives that failure to raise the debt limit would probably ensure Obama's re-election in 2012. He predicted that a default would allow Obama to argue that Republicans were making the economy worse.

"You know, it's an argument he has a good chance of winning, and all of a sudden we (Republicans) have co-ownership of a bad economy," McConnell said. "That's a very bad positioning going into an election."

The proposal won praise from two disparate points in the political spectrum — Republican Sen. John McCain of Arizona and Democratic leader Reid of Nevada.

Reid said it's "a serious proposal. And I commend the Republican leader for coming forward."

Sen. Charles Schumer, D-N.Y., said Thursday that while the president and other Democrats would still prefer a larger agreement, McConnell's plan is an acceptable option — especially if some consensus spending cuts are added to it. He said McConnell and Reid were discussing the idea.

Democratic officials said that even as Obama confronted Cantor and Boehner in Wednesday's meeting, he commended McConnell.

"Sen. McConnell at least has put forth a proposal," a Democratic official quoted the president as saying. "It doesn't reduce the deficit and that's what we have to do. It just deals with the debt limit. Now Sen. McConnell wants me to wear the jacket for that."

The officials said Obama went on to say they all had a responsibility to find a compromise.

Overall, Cantor says, the White House has been lowering the amount of spending cuts on the table, offering less than $1.4 trillion over 10 years, mostly in domestic and defense spending outside of the major benefits programs Medicare, Medicaid and Social Security.

The White House says the total is closer to $1.7 trillion over 10 years when counting about $240 billion in reduced interest payments from the lowered debt.

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Associated Press writers Dave Espo, Laurie Kellman, Ben Feller and Erica Werner in Washington and Pallavi Gogoi in New York contributed to this report.