Senate Democrats unveiled yesterday a likely-doomed plan to offset “sequestration” budget cuts through the end of December with a package of new revenues and budget cuts, including a $27.5 billion multi-year defense reduction.

Democrats released broad outlines of the proposal, dubbed the American Family Economic Protection Act, just as Congress prepared to recess for a week and then return to Washington the final week before the cuts are slated to start March 1.

Their plan would replace sequestration–$1.2 trillion in decade-long cuts to defense and non-defense spending–until Jan. 2, 2014, with an equal share of revenues and cuts. It has “half of the spending cuts coming on the defense side in a way the Pentagon can implement responsibly,” according to a Senate Budget Committee fact sheet released yesterday afternoon.

Observers said the Democratic plan appears to be yet another partisan proposal in Congress to counter sequestration that the opposing party will dismiss. When talking about what they want in a plan to replace sequestration–which is widely, but not universally, unpopular in Washington–Republicans have rejected new revenues. Some hawkish GOP lawmakers, particularly in the House, have insisted a replacement plan include no additional defense cuts.

Senate Minority Leader Mitch McConnell (R-Ky.) dismissed the Democrats’ proposal, in advance of its release, as “a total waste of time,” charging the revenue-generators in it are a “gimmicky tax hike.” He faulted Democrats for waiting “right up to the moment of crisis” to present the proposal. He repeated his message from earlier this week that he will not relent and agree to a last-minute compromise plan with Democrats that includes more revenues, as Republicans already did in the final days of 2012 to prevent the so-called “fiscal cliff.”

“There won’t be any easy off-ramps on this one,” McConnell said yesterday. “The days of 11th hour negotiations are over.”

Budget Committee Chairwoman Patty Murray (D-Wash.) told reporters yesterday at the Capitol that Senate Democrats “all feel very strongly that…50-50 (split between cuts and new revenue) is a fair and balanced way to move forward.”

“We’re putting forward a responsible plan, the Republicans are saying, ‘No, let it take effect,’” she said about the looming cuts. She brushed off criticism that the proposal is coming too late, with only four legislative days left before sequestration is due to start March 1.

“We have a week and a half right now to get the public support with us, and I know they’re going to be with us as they see that we’re being responsible,” she said after a closed-door meeting of Senate Democrats.

Many lawmakers and aides predict if sequestration starts Congress will agree on a plan to avert it when it addresses the federal budget, which is now funded through a bare-bones continuing resolution that expires March 27.

The Senate Democrats’ plan calls for $27.5 billion in “responsible” defense cuts and the same amount of cuts to agricultural spending. Though the legislation would pay to stop 10 months of sequestration cuts, the replacement defense savings would be stretched out over multiple years.

“The American Family Economic Protection Act includes modest reductions in the overall level of defense spending phased in responsibly to time with the troop drawdown in Afghanistan in 2015, and continuing through 2021,” the Budget Committee fact sheet says. “The reduction would be about $3 billion in Fiscal Years 2015 and 2016, and then would rise slowly to a high of about $5 billion in Fiscal Year 2021.”

If sequestration starts on March 1, defense spending would reduce by a projected $46 billion until the end of fiscal year 2013 on Sept. 30.

The Senate Democrats’ plan also calls for garnering $55 billion in new revenue “from the wealthiest Americans and biggest corporations.” It would install the so-called Buffett Rule for high-income earners while also ending tax breaks for companies that move jobs overseas and tax loopholes used by oil companies.

House Republicans also have insisted they will not accept a sequestration compromise with Democrats that includes new revenues. The GOP-led House Rules Committee on Wednesday rejected a Democratic amendment–to a bill before the House on federal employees’ pay–that would replace the sequestration cuts this year through steps including increasing taxes for wealthy Americans and ending subsidies for oil companies.

In addition, the House Appropriations Committee is working on a government-funding package for the final months of FY ’13 that does not stop sequestration. That appropriations legislation includes a full-blown FY ‘13 appropriations bill, to which House and Senate appropriators already have agreed.