The U.S. Capitol stands in Washington, D.C., U.S., on Thursday, Nov. 14, 2013. (Andrew Harrer/Bloomberg)

After compiling a reed-thin record of achievement for 2013, the House and Senate began their final week of the year together in Washington on the verge of breakthroughs on a new defense policy bill and budget agreement, deals that could permit lawmakers to boast of modest year-end successes and enjoy their first extended Christmas break since at least the start of the Obama presidency.

Speaker John A. Boehner (R-Ohio) is determined to adjourn the House for the year on Friday. The Senate plans on remaining in town until Dec. 20. It is a short schedule that forced leaders of the House and Senate armed-services committees Monday to scale back their ambitions and agree to move ahead with a modified version of the National Defense Authorization Act, one of the few “must pass” measures left for the divided Congress.

If passed, the modified bill would provide a modest pay increase for military service members and authorize combat pay and hardship pay for troops deployed in battle. The measure also would bar the Obama administration from transferring terrorism detainees at the U.S. military base in Guantanamo Bay, Cuba, to facilities in the United States and provide funding for the destruction of Syria’s chemical-weapons stockpile.

In an attempt to end the rising scourge of sexual assault in the ranks, the defense bill also would make sweeping changes to military personnel policy by ending the statute of limitations on such offenses; requiring the dishonorable discharge or dismissal of anyone convicted of sexual assault; and stop military commanders from modifying the findings of military prosecutors.

The defense bill is logjammed in the Senate, where lawmakers have failed to agree on a series of proposed amendments. With no hope of resolving disagreements over dozens of proposed changes to the original defense bill, negotiators agreed Monday that the House will vote on a modified version of the bill before leaving Friday and send it to the Senate, where it could be approved next week — ensuring that Congress passes the legislation for the 52nd consecutive year.

@TheBudgetGuy Stan Collender tells Chris Cillizza what the much-anticipated budget deadline has in common with the hit nineties television show. (The Washington Post)

“This is not the best way to proceed,” Senate Armed Services Committee Chairman Carl Levin (D-Mich.) said in a floor speech. “But our troops and their families and our nation’s security deserve a defense bill, and this is the only practical way to do a defense bill this year.”

The decision to proceed with a modified defense bill means that a series of more-ambitious proposals by Sen. Kirsten Gillibrand (D-N.Y.) to rewrite military personnel rules will be considered as a stand-alone measure at some point next year.

The agreement on the defense measure came as Senate Majority Leader Harry M. Reid (D-Nev.) welcomed colleagues back for what he said he hopes will be “a short, two-week work period.” But he threatened — as he often does — to keep the chamber open over the next two weekends to complete a litany of tasks, including passage of a new budget and a farm bill. He also listed the possibility of debating a new round of sanctions against Iran, as well as plans to confirm new leaders at the Department of Homeland Security and the Federal Reserve.

Monday evening, the Senate quickly moved to reauthorize a federal ban on the manufacturing of plastic guns that are not detectable by security-screening devices — making it the first federal gun legislation approved by Congress since the massacre at a school in Newtown, Conn., last December. The House reauthorized the ban last week.

On the budget, lawmakers were especially hopeful of reaching an agreement by Friday. House and Senate negotiators working on the deal were preparing to brief colleagues by midweek on their proposal to fund the government past Jan. 15, aides said — though the winter weather and absences for the funeral of former South African president Nelson Mandela could delay the rollout, they said.

Work appeared to be complete on the basic package, a plan to partially repeal sharp spending cuts known as the sequester in fiscal 2014 and 2015 and cover the cost with roughly $65 billion in alternative savings. But Senate Budget Committee Chairman Patty Murray (D-Wash.) and House Budget Committee Chairman Paul Ryan (R-Wis.) were conferring with congressional leaders on other year-end issues, including the expiration of benefits for the long-term unemployed and payment rates for doctors who see Medicare patients.

It was unclear Monday whether Democrats would succeed in their campaign to win a year-long extension of emergency jobless benefits, which are set to expire at the end of the month, cutting off 1.3 million people. People familiar with the talks said there was no certainty, either, about Medicare reimbursement rates. Unless Congress acts, doctors will have to absorb a 24 percent pay cut in January.

Though details of the agreement are closely held, opponents on the right and left are already lining up to torch it.

On Monday, the influential conservative group Heritage Action for America issued a statement saying it “cannot support a budget deal that would increase spending in the near-term for promises of woefully inadequate long-term reductions.” The conservative Club for Growth, which also wields considerable influence in the GOP, declined to comment on the emerging agreement.

Liberals, meanwhile, were stewing about unemployment benefits and potential cuts to federal-worker pensions. Speaking on MSNBC, Rep. Chris Van Hollen (D-Md.) agreed that a hit to federal-worker pensions would be a “deal-breaker” for him.

“You cannot be asking federal employees to bear the share of the burden that they’re asking for here as part of an agreement when you’re not asking, for example, agribusinesses that get huge taxpayer subsidies to have a contribution toward the deal,” Van Hollen said.

Ryan and Murray were rushing to put the finishing touches on their package and quickly bring it to a vote in the House. Absent an agreement to fund federal agencies through fiscal 2014, Congress risks another government shutdown when the current temporary funding measure expires Jan. 15.