WASHINGTON — Leading Congressional Democrats immediately recoiled Tuesday from a new proposal to cut $600 billion in Medicare spending over the next decade, in part by raising the eligibility age.

Sens. Joe Lieberman, I-Conn., and Tom Coburn, R-Olka., unveiled the proposal as part of a bipartisan effort to produce the kind of savings necessary to achieve the $2 trillion in debt reduction both parties say is needed to convince reticent lawmakers to vote to raise the debt ceiling.

The plan would raise Medicare’s eligibility age from 65 to 67 and assess higher premiums on wealthier seniors.

The proposal echoes Republican demands that entitlement reform – especially deep cuts in Medicare spending – be a part of any agreement to raise the nation’s debt ceiling.

But the swift rejection of the proposal among Democrats reflects the significant obstacles that remain to any agreement to cut the deficit and raise the nation’s legal borrowing limit.

Positions on both sides have been hardening in recent days, as an Aug. 2 deadline approaches for working out a deal before the nation defaults on its obligations.

A previously scheduled White House meeting with top Senate Democrats today will likely be devoted to the negotiations.

Republican leaders in the House and Senate have said there can’t be more progress in negotiations until Democrats agree to entitlement cuts and forgo any new taxes.

Senate Minority Leader Mitch McConnell, R-Ky., who met Monday with President Obama and Vice President Biden at the White House, said no additional talks had yet been scheduled.

Democrats insist that the deficit cannot be reduced by cutting spending alone. No deal is possible, they say, without an agreement to close tax loopholes that benefit the wealthy, including subsidies for major oil companies and a tax break provided to companies that buy private jets.

And they have promised they will not trim benefits to Medicare beneficiaries, a point underscored by their chilly reception of the plan advanced by Lieberman and Coburn.

The two senators conceded that their plan would be unpopular but said it presented the prescription to long-term health for the federal program.

“Our plan contains some strong medicine but that’s what it will take to keep Medicare alive. But we believe our plan administers that medicine in a fair way,” Lieberman said. “It asks just about everybody to give something to help preserve Medicare. But it asks wealthier Americans to give more than those who have less.”

With polls showing Medicare cuts deeply unpopular and a restive base anxious that their party may give away too much to achieve a debt deal, Democratic rejection of the proposal was swift.

Senate Majority Leader Harry Reid, D-Nev., termed it “a bad idea.”