WASHINGTON — Year-end legislation to ease Congress’s chronic budget brinkmanship and soften across-the-board spending cuts passed a test vote in the Senate Tuesday and moved to the cusp of final passage.
Tuesday’s vote to send the measure toward final approval was 67 to 33, more than enough to break a filibuster.
It was a rare display of Senate bipartisanship that masked strong Republican complaints about slicing into military retirement benefits.
The measure is expected to clear the Senate and go to President Obama on Wednesday. A simple, 51-vote majority is required for passage.
The compromise marked a modest accomplishment at the end of a year that was punctuated by a partial government shutdown, a near-default by the US Treasury, and congressional gridlock on issues ranging from immigration to gun control.
‘‘This bipartisan bill takes the first steps toward rebuilding our broken budget process. And, hopefully, toward rebuilding our broken Congress,’’ said Senator Patty Murray, Democrat of Washington, who negotiated the compromise with Representative Paul Ryan, Republican of Wisconsin.
The first major test of that is likely to come in February, when Congress faces a vote to raise the government’s debt limit.
Even as the bill was advancing, Republicans vowed that the requirement for curtailing the growth in cost-of-living benefits for military retirees under age 62 wouldn’t long survive.
The Democratic chairman of the Senate Armed Services Committee, Senator Carl Levin of Michigan, has said the panel will review the change, estimated to trim some $6.3 billion in benefits, early next year.
‘‘This provision is absolutely wrong; it singles out our military retirees,’’ protested Senator Kelly Ayotte, Republican of New Hampshire, at a news conference shortly before the vote.
By late afternoon, the bipartisanship had faded as Republicans ratcheted up their criticism and maneuvered for political gain.
A proposal aimed at removing the retirement provision failed on a near party-line vote of 46 to 54. Democratic Senator Kay Hagan of North Carolina, who faces a difficult challenge for reelection, was the only senator to switch sides.
‘‘How could any commander in chief sign a bill that does this,’’ said Senator Lindsey Graham, Republican of South Carolina, who faces a primary challenge back home in 2014.
He did not mention that the legislation drew overwhelming support from House Republicans only last week, including Speaker John A. Boehner, Republican of Ohio, and the rest of the leadership.
The provision related to military retirement was a relatively small part of legislation that itself was born of less-than-lofty ambitions.
Rather than reaching for a so-called grand bargain to reduce long-term deficits, lawmakers decided to reduce across-the-board cuts already scheduled to take effect, restoring about $63 billion over two years. The legislation includes a projected $85 billion in savings elsewhere in the budget.
Because spending would rise immediately but many of the savings would take place later in the decade, deficits would increase as a result of the measure for the current budget year and the two that follow.
Over the 10-year period, the legislation shows a $23 billion cut in red ink — a trifle compared with the government’s overall debt of more than $17 trillion and rising.
Graham was far from the only senator criticizing the military-retirement provision.
Senator John McCain, Republican of Arizona, said he was voting for the legislation because it would cancel a $20 billion cut that would hit the Pentagon in January — and with the knowledge that the retirement provision could be changed before it took effect.
All three voted against advancing the bill, but Republicans who were on the other side said they, too, were expecting lawmakers to reconsider the retirement action in 2014.
‘‘That gives some of us some comfort,’’ said Senator Rob Portman, Republican of Ohio, one of 12 GOP senators to side with all 53 Democrats and two independents in voting to ease the measure over a 60-vote threshold.
It had been clear for several days that the overall measure was headed for Senate passage, particularly after the Republican-controlled House had voted overwhelmingly last week to approve it.