Democrats on Friday rejected a last-ditch bid by Republicans to save the congressional supercommittee from failure, leaving the panel with no apparent path to compromise as the clock ticks toward a Thanksgiving deadline.

Having concluded that agreement looks increasingly unlikely on a far-reaching plan to raise taxes and restrain social spending, Republican members of the supercommittee worked with House Speaker John A. Boehner (R-Ohio) to develop a smaller “Plan B” that would stop far short of the panel’s goal of $1.2 trillion in deficit reduction over the next decade.

Instead, Republicans proposed to achieve $640 billion in savings, primarily through cuts to domestic agency budgets, a pay freeze and bigger pension contributions for federal workers, cuts in farm subsidies and an array of other spending cuts and revenue raisers.

The offer, delivered Thursday to Senate Majority Leader Harry Reid (D-Nev.), included no cuts to the Pentagon other than attrition in the civilian workforce. It also included just one small tax increase, focused on owners of corporate jets, failing two key tests for Democratic negotiators.

Republican leadership aides said Democrats immediately rejected it.

“Now, our [supercommittee] Members continue to talk among themselves and with their Democratic colleagues about ways to reach the committee’s goal, and whether Democrats will agree to ANY spending cuts without job-killing tax hikes,” a GOP leadership aide said in an e-mail, speaking on condition of anonymity to discuss private negotiations.

Democratic aides said the proposal would have reduced sharp cuts to defense that are scheduled to take effect in 2013 if the supercommittee fails and replaced them with cuts that would affect the middle class.

As he left the Capitol Friday afternoon, Reid merely smiled when asked about the Republican offer.

“I’m going to be available to talk, if they’re willing to put forward something reasonable. If they’re not willing to put forward anything reasonable, there’s no point in talking,” he said.