Senate Minority Leader Mitch McConnell (R-Ky.) on Tuesday unveiled a “back-up plan” for raising the debt ceiling in case the ongoing negotiations between congressional leaders and the White House fail to produce a result by an Aug. 2 deadline.

At a Capitol news conference little over an hour before the latest round of negotiations was set to begin at the White House, McConnell described a plan that would allow the debt ceiling to be raised in three separate stages through the end of next year, for a total of $2.5 trillion. The plan would place the political burden of raising the debt limit on President Obama and congressional Democrats, rather than on Republicans.

“If the White House talks lead not to a conclusion that we can go forward together to reduce spending, which is our single biggest problem, then what is the alternative?” McConnell said. “So what I’ve told my members is that we will have available a back-up plan that would operate as follows.”

The first part of the plan would entail Obama submitting a request to Congress to raise the debt ceiling by $700 billion ahead of the Aug. 2 deadline. Then, Congress could pass a resolution of disapproval; the president could either sign it or veto it, McConnell said.

“Presumably, he would veto it,” McConnell continued. “If that were the case, that veto would be sustained by one-third-plus-one in either the House or the Senate.”

The second debt-limit request, for $900 billion, would then likely come in the fall of 2011 and would follow the same procedure, McConnell said. The third, another $900 billion increase, would come in the summer of 2012 and would lift the debt ceiling through the end of the year.

Along with each debt-limit increase, Obama would be required to submit a proposal for spending cuts greater than or equal to the figure by which the ceiling was raised – a move that would be in line with House Speaker John Boehner’s (R-Ohio) position in the debt-limit talks.

Full details were not yet available as of Tuesday afternoon — and the proposal would likely be subject to approval by both chambers of Congress — but it appeared that the proposal would allow for the debt limit to be raised without locking in those spending cuts, something that could draw opposition from the Republican rank-and-file.

In a boon for Republicans, however, the proposal would place the debt-limit ball in Obama’s court and would also force congressional Democrats to shoulder the political burden of voting to increase the country’s borrowing limit multiple times before the 2012 election.

Senate Minority Whip Jon Kyl (R-Ariz.), who also spoke at Tuesday’s news conference, said that the plan came about after the White House balked at some of the deficit savings that had already been identified over the course of negotiations led by Vice President Biden over the past two months.

“What the leader and I have concluded after the meeting on Sunday and particularly the meeting yesterday is that the administration is now even walking away from agreements that we had tentatively made during the debt-limit talks with Vice President Biden,” Kyl said. “To be clear, there was an understanding that there would be no agreement on anything until everything was agreed to, but it is also the case that we had agreed on a significant amount of savings in the neighborhood of about $500 billion that, all else being equal, we could show the American people that could be saved.”

He added, “When the administration walked away from much of that yesterday afternoon, it became clear to us that we’d better be thinking about an alternative in the event that we couldn’t reach an agreement.”

The move by McConnell comes as Obama, in an interview with CBS News set to air Tuesday evening, said that he “cannot guarantee” that Social Security checks will be issued if Congress fails to raise the debt ceiling by Aug. 2.

“I cannot guarantee that those checks go out on Aug. 3 if we haven’t resolved this issue, because there may simply not be the money in the coffers to do it,” Obama said, according to advance excerpts of the interview.

McConnell deputy chief of staff Don Stewart said that Obama’s “threats about Social Security are no longer real if this bill passes.”

Stewart also told reporters that the Republican leader had already discussed the proposal with Boehner.

“The Speaker shares the Leader’s frustration,” Boehner spokesman Michael Steel said in a statement. “Republicans are unified in our commitment to ensuring that the debt limit is not used as leverage to saddle small businesses with increased taxes that destroy jobs.”