WASHINGTON — House Republican leaders spent Monday trying to finalize a plan to increase the Treasury’s borrowing authority and avoid a federal default by urging GOP lawmakers to rally behind a proposal that ties a debt-ceiling increase to a plan to restore full pension benefits for some military veterans.

House Speaker John Boehner, R-Ohio, called a “special conference meeting” in the Capitol basement, trying to find the right policy mix that would attract enough Republican and Democratic support for the measure to be approved, possibly as soon as Wednesday.

Republicans exiting the meeting stressed that Boehner’s team had made no final decision and that the proposal’s fate remained uncertain. “I believe we are on track,” said House Majority Leader Eric Cantor, R-Va. “We had a really good discussion. We are going to talk to our members and work toward a resolution.”

Still in place is a backstop option that would essentially allow Democrats to approve a debt-limit hike with no strings attached, almost entirely on their own, according to GOP advisers.

Despite the uncertain fate, Boehner’s team moved ahead with the option linking a restoration of recently cut military pension benefits to a one-year extension of the Treasury’s borrowing authority. The cost of restoring that cut to military pensions, about $7 billion, would be offset by an extension, by one year, of planned automatic spending cuts to entitlement programs.

Republicans have been trying to finish the plan before the House adjourns Wednesday for a nearly two-week break. That would keep them from bumping up against the Feb. 27 date that Treasury Secretary Jack Lew has set as the deadline for Congress to increase his borrowing authority or risk a default on the more than $17 trillion in federal debt.

Whatever the outcome, Boehner’s proposal marked a stark retreat from the confrontational approach Republicans adopted in 2011, when the speaker rung $2.1 trillion in savings out of federal agency budgets from President Barack Obama in exchange for increasing the debt limit.

Lawmakers said Boehner and Cantor told them there was no debt proposal that could win a majority solely from the GOP side of the aisle. “I made my feelings clear – we should fight,” said Rep. Andy Harris, R-Md. “There will be a vote on Wednesday and I sure know how I’m going to vote, and that’s firmly against the package.”

The new offer drew pointed criticism from conservative lawmakers and groups that have caused constant headaches for Boehner. “I think that’s the wrong place to go,” Rep. Jim Jordan, R-Ohio, a leading member of the House’s right flank, said of the proposal. “Obviously, we should honor our commitment to our veterans, but let’s do that in a separate bill and find savings elsewhere. I don’t think we should tie it to the debt ceiling, and I think other members will agree.”

Michael Needham, chief executive of Heritage Action for America, an influential conservative advocacy group on Capitol Hill, said Monday that his organization would probably oppose the measure, should it reach the floor.

But the criticism was combined with a general shrug from many conservatives who seem resigned to a debt hike happening.

Heritage Action has not mounted a campaign to push the leadership to move to the right, unlike in past fiscal battles when the group trimmed Boehner’s options through a pressure campaign from its grass-roots network.

Grover Norquist, the prominent anti-tax advocate, rejected any tinkering with a budget deal agreed to two months ago that included the savings from a slight reduction in the cost-of-living adjustment for pension plans of military veterans who are still working age. “Let a clean bill through without touching the spending restraints established in these budget agreements,” Norquist, president of Americans for Tax Reform, said in an interview.