Congress is facing pressure to reauthorize funding for a key, decadeslong conservation program for national parks after letting it expire Sunday.

Bills are progressing through the House and Senate to re-up funding for the Land and Water Conservation Fund, which has broad bipartisan support. But lawmakers couldn’t finish the deal in time, angering environmentalists.

“Late last night, one of the most successful conservation programs in American history expired due to the negligence of Congress,” said Diane Regas, president and CEO of The Trust for Public Land. “This is a big disappointment.”

The Land and Water Conservation Fund gets its money from offshore oil and gas leases, rather than taxpayer money, and pays for public lands projects. It provides money to federal, state, and local governments for buying land and waters to improve parks, forests, wildlife refuges, and other public areas.

The fund still has $39 billion in it, the Interior Department said, enough to spend on projects. However, it cannot generate new money until Congress acts. Money normally raised from offshore oil and gas drilling will instead go to the general fund. Congress will likely act after Election Day, since the House is out of session until then.

The fund hasn't progressed despite the fact that leaders of the House Natural Resources Committee reached a much-celebrated deal last month to save the program.

Reps. Rob Bishop of Utah and Raul Grijalva of Arizona, the Republican chairman and top Democrat of the House committee who usually feud about public lands issues, co-authored legislation to permanently reauthorize the program, so Congress doesn’t have to deal with a potential lapse of the fund.

The committee quickly approved the bill. But Bishop on Monday put down conditions for what he would support on the House floor. He said Congress should consider reauthorizing the program as part of a broader public lands package that would also fund repairs and maintenance in the country's national parks.

“LWCF can and will be reauthorized,” Bishop said in a statement. “The best path forward is to include it in a broader legislative lands package that addresses the National Park maintenance backlog and other lands related measures.”

His committee last month approved a bipartisan bill backed by the Trump administration that would pay for billions of dollars in repairs with money the government collects from the development of oil, natural gas, wind, and solar energy on public lands. Bishop and Grijalva co-sponsored the bill.

Grijalva, however, signaled Monday that he would prefer Congress reauthorize the Land and Water Conservation Fund as a stand-alone measure.

“The worst outcome would be for Republican leadership to hold LWCF hostage as a way to advance their unrelated, controversial priorities," Grijalva said in a statement. “Now is not the time to tie LWCF’s fate to bills that can’t pass Congress on their own steam. Let’s pass LWCF as soon as we get back in session and handle other issues as they arise.”

The Senate, meanwhile, is on a separate track to move legislation re-upping the Land and Water Conservation Fund. The Senate Energy and Natural Resources Committee as soon as Tuesday could vote on bipartisan legislation sponsored by Sen. Maria Cantwell of Washington, the panel’s top Democrat, that would make the program mandatory and not make it subject to the regular appropriations process.

Bishop does not favor that approach, and other House conservatives will likely follow his lead.