WASHINGTON - Key lawmakers weighed legislation to permit a reduction of benefits for up to one million retirees at economically distressed multiemployer pension plans, officials said late Monday as Congress labored over a $1.1 trillion measure to keep the government operating past midnight Thursday.

The officials said the goal of the secretive pension talks was to preserve benefits as much as possible and avert bankruptcies at troubled plans that could in turn endanger the stability of the federal Pension Benefit Guaranty Corp.

Few details of the proposed changes under discussion were available. Republicans and Democrats on the House Education and Workforce Committee issued a statement that said lawmakers "are still discussing the details about a possible legislative solution to the multiemployer pension crisis and remain hopeful Congress will act before the end of the year."

Proposed changes have the support of many of the multiemployer pension plans in financial difficulty, but has drawn opposition from other, healthier entities.

The officials who provided further information did so on condition of anonymity, saying they were not authorized to preempt a formal announcement. The PBGC website says multiemployer plans result from collective bargaining between a labor union and more than one company.

The issue was among numerous items affecting the final shape of the spending measure, one of a handful of must-pass items clogging the agenda for lawmakers eager to adjourn for the new year.

Others were bills to extend dozens of expiring tax breaks, authorize President Obama's policy of arming Syrian rebels to fight Islamic State forces, and a Democratic drive to confirm as many administration nominees as possible before the Republicans take control of the Senate in January.

Legislation to continue preventing state or local governments from imposing a tax on Internet access also seems likely to make it to Obama's desk.

There was relatively little controversy over spending levels themselves in what was shaping up as a classic year-end measure that rolled numerous unrelated issues into a single package. The $1.1 trillion in total spending adhered to spending caps approved in previous negotiations between Obama and House Republicans. It included more than $5 billion of the $6.2 billion the president requested to fight Ebola at home and overseas.

The money would be available to keep the government running through the Sept. 30, 2015, end of the fiscal year, except for the Department of Homeland Security, which oversees border security programs. Even failure to complete work before Thursday at midnight would not lead to a government shutdown, since lawmakers were prepared to pass a stopgap bill for a day or two to make sure there was no interruption in federal services.