Eleven major environmental groups said they wouldn't support bipartisan energy legislation that will be taken up Tuesday in the Senate Energy and Natural Resources Committee unless changes are made.

The groups said in a letter to bill co-sponsors Sens. Lisa Murkowski, R-Alaska, chairwoman of the panel, and top Democrat Maria Cantwell, of Washington, that provisions to nix a phase-out of fossil fuels in federal facilities by 2030, delay a furnace efficiency rule, remove some permitting requirements for hydropower projects and impose a timeline on approving liquefied natural gas exports were non-starters, among other issues.

"Authoring a bill of such complexity in a bipartisan manner is a truly impressive accomplishment, but that does not justify removing key environmental protections," the groups, which include the Natural Resources Defense Council, Sierra Club, League of Conservation Voters, Environmental Defense Fund and others, said in a letter Monday.

The letter is a setback for Murkowski and Cantwell, who negotiated the 357-page bill over several months with input from other lawmakers and several hearings.

Getting the legislation through the Senate always figured to be tricky, given senators' penchant for pushing amendments on the sparse number of bills that hit the chamber's floor. The environmental groups noted in their letter that "numerous amendments have been filed," and they urged Murkowski and Cantwell to "block any amendments that will jeopardize our climate, air, water, land, wildlife and bedrock environmental laws."

The Senate bill goes further than a similar House bill — the House version, for example, doesn't include the measures on hydropower, natural gas exports and the fossil fuel phase-out — that environmental groups have raised objections to, albeit less formally.

The bill avoids many of the more contentious energy issues in Congress. It doesn't include a section on climate change, though Murkowski told reporters last week that the policies it would green light, such as several energy-efficiency items, would reduce emissions, nor does it touch on whether to end the 40-year-old ban on exporting crude oil.

But environmental groups said they want the bill to more explicitly address climate change and clean energy investment. They also raised concerns that some elements of the bill, such as allowing electric generators to violate environmental laws in the case of war or a widespread electric reliability emergency, would raise emissions.

"[W]ithout a stronger vision for accelerating the development and deployment of clean energy resources this bill may prove a missed opportunity," the letter said.