The House of Representatives is expected to approve back pay this month for hundreds of thousands of federal contractors who went unpaid during the 35-day government shutdown during December and January, according to Democratic lawmakers.

On Tuesday, the House Appropriations Committee announced that an upcoming government spending package will include back pay for an estimated 580,000 federal contractors, whose ranks include among the lowest-paid workers, such as janitors, security guards and cooks.

The legislation is likely to clear the House in June — possibly in two weeks’ time — as part of a broader package that includes funding for the Agriculture, Commerce, Justice and Interior departments, according to a House Democratic aide granted anonymity to discuss internal deliberations.

[The lowest-paid shutdown workers aren’t getting back pay]

House and Senate negotiators will then have to resolve differences in their spending proposals, and the plan’s fate at that juncture remains unclear. On Wednesday, a Senate Republican on the Appropriations Committee expressed doubt about the effort.

During the shutdown, President Trump and Congress approved a measure ensuring back pay for federal employees — a measure that left out the federal contractors. Union leaders say these contractors generally earn between $460 and $650 weekly, making them among the lowest-paid government workers. Many of these employees worked through the government shutdown despite the lack of pay.

“The federal government relies on these hard-working men and women — our security professionals, our food service workers, our custodial workers — to keep our government buildings running,” Rep. Ayanna Pressley (D-Mass.), who helped lead the push for the back pay along with Sen. Tina Smith (D-Minn.), said in a statement. “By including back pay in the upcoming spending package, we are one step closer to finally giving our federal contractor employees what they are owed.”

A group of Senate Democrats joined by Sen. Susan Collins (R-Maine) have also urged Senate leaders to approve contractor back pay. But their efforts have languished for months, frustrating those who depend on routine checks of the federal government. And another government impasse looms: Lawmakers have until September to pass 12 appropriations bills or risk another shutdown. Top Senate officials, including Appropriations Committee Chairman Richard C. Shelby (R-Ala.) and Majority Leader Mitch McConnell (R-Ky.), were scheduled to meet Wednesday afternoon with top White House officials about the budget, according to a Senate Republican aide.

Sen. James Lankford (R-Okla.), an Appropriations Committee member, said he needed to see details of the House plan but expressed concern about the feasibility of determining exactly which federal contractors should be eligible for back pay.

“Once you open that up, it’s obviously trying to identify every janitorial service, every independent contractor — you have some consistent people, but you also have people who come in and out,” Lankford said, adding that he is working on legislation to end government shutdowns. “That’s always been the hard part.”

Some companies and union leaders have said they suffered long-lasting effects from the shutdown, which Standard & Poor’s estimated cost the U.S. economy $6 billion. Roger A. Krone, chairman and CEO of the defense contractor Leidos, told a House panel last month that his firm lost $14 million because of the shutdown. The shutdown also stalled or stopped 22 programs “of significant importance to our country,” Krone said.

“Many of our colleagues took it on the chin, quietly eroding their savings, stopping investment deposits, canceling planned trips or down time, and even dipping into retirement accounts,” Krone told a House subcommittee on government operations.

The shutdown also makes it harder for federal contractors to recruit and retain talented employees, according to the House testimony of David J. Berteau, president and CEO of the Professional Services Council, which represents hundreds of government technology and service industry companies.

Workers reported going into debt, erasing their savings, and relying on churches and relatives for meals. Hector Figueroa, president of the union 32BJ, which represents many of these workers, said in an email that many of the men and women “are still behind on rent and bills they accrued while they were out of work for an entire month.”

“Before Trump brings our government to the brink of yet another shutdown, we must not let one more day go by without righting this wrong,” Figueroa added.