WASHINGTON — Facing a standoff in the Senate, the top Democrats and Republicans on Congress’ military panels are working on a backup plan to ensure that they complete a far-reaching defense policy bill before year’s end.

Rep. Howard "Buck" McKeon, R-Calif., chairman of the House Armed Services Committee, and the panel’s top Democrat, Rep. Adam Smith of Washington state, expressed optimism on Thursday that they could agree with their Senate counterparts on a pared-back bill that would cover a pay raise for troops, buy new ships and aircraft and address the epidemic of sexual assault in the military.

The Senate and the House have only one legislative week to work out their differences before the House adjourns for the year on Dec. 13. A version of the bill remains stalled in the Senate, caught up in a dispute over amendments.

"We have to have this done," Smith told reporters. "A whole lot of bad stuff happens if we don’t pass this by the end of the year, in terms of military pay, in terms of death benefit compensation, in terms of military construction projects and on and on and on."

Under the fallback plan, the House would quickly pass a new, precooked bill and send it to the Senate.

Although the Senate could change it, any move would jeopardize swift action with no time for the House to accept those changes. Ideally, Smith said, the Senate would approve the new House-passed bill without amendments and send it to President Barack Obama for his signature before the end of December.

This process means some of the more controversial issues that the Senate wants to vote on would have to wait until next year, including a new round of sanctions on Iran, steps to rein in the National Security Agency’s spying and aid to Egypt.

Asked what would be the path forward for completing a bill this year, McKeon said simply, "The Senate."

The defense bill is one of several items in a busy year-end agenda for Congress that also includes a budget bill and renewal of food stamps and farm programs. Congressional negotiators are pursuing a modest deal before year-end to ease the automatic spending cuts that are squeezing both the Pentagon and domestic federal programs.

House Democratic leader Nancy Pelosi said Thursday she would withhold support from any compromise to ease across-the-board cuts until Republicans also agree to renew expiring unemployment benefits for the long-term jobless, adding a major complication. At the same time, conservatives are balking at a proposal to raise fees on airline tickets to pay for TSA agents as part of an agreement, another hurdle.

GOP leaders, meanwhile, are preparing a backup plan for averting another government shutdown in January if there’s no budget deal by then.

The Obama administration wants to avoid any congressional votes on a new batch of tough penalties on Iran just weeks after world powers announced a deal to temporarily freeze Iran’s nuclear program. At this point, no votes are expected, but a clearer picture will emerge when the Senate returns next week.

Smith said contentious issues that were in the House bill that passed in June or in the Senate bill approved by the Armed Services Committee this past summer could end up in the new, stripped-down bill. Among them would be how to handle terror suspects held at the detention center at Guantanamo Bay, Cuba, and steps on dealing with sexual assault in the ranks.

"Iran sanctions was not in either bill so we can’t airdrop (that) in," Smith said.

Last month, Senate Majority Leader Harry Reid, D-Nev., was determined to avoid a vote on sanctions as negotiators held talks in Switzerland. Reid also wasn’t keen on replaying a fight over the health care law, opening up contentious issues such as government spying or allowing probably the last bill out of Congress this year to become a magnet for other matters.

"Everyone has to understand this is not going to be an open amendment process," Reid told his colleagues as he sought to limit amendments and wrap up the $625 billion defense measure after some three days of debate.

That stance was described as a power grab by frustrated Republicans who demanded they be allowed to offer amendments and get votes on them — the norm for decades on a bill that represents half the nation’s discretionary budget.

That stalled the bill, the latest traditionally bipartisan measure to fall on the hard times of a fractious Congress.

McKeon, who is in talks with Sen. Carl Levin, D-Mich., chairman of the Senate Armed Services Committee, and the panel’s top Republican, Sen. Jim Inhofe of Oklahoma, said he was confident about getting a deal on a new bill.

Not only is the defense policy measure at stake, but lawmakers’ streak. Congress has passed a defense authorization bill for 51 years straight.

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Associated Press writer Andrew Taylor contributed to this report.