Sens. John Kerry (D-Mass.) and Joe Lieberman (ID-Conn.) plan to huddle privately this afternoon with environmental groups to discuss progress on a slimmed-down energy bill. The Members’ meeting with the activists comes as momentum for the stalled energy and climate legislation has been revived in the Senate after the oil spill in the Gulf of Mexico.

Representatives for the National Resources Defense Council, Center for American Progress, World Wildlife Fund, Sierra Club, Environmental Defense Fund, Union of Concerned Scientists and Alliance for Climate Protection are all expected to attend, sources said.

Making sure environmentalists are on board with a pared-down bill is a key to winning over more liberal lawmakers who would like the bill to go further.

“The litmus test is: Does it have a limit on carbon in some form, most likely the utility sector at the minimum and hopefully beyond that?” the EDF’s Tony Kreindler said.

Kerry and Lieberman are expected to discuss a three-pronged approach that includes increasing renewable electricity and clean technology development, a framework for what the government’s oil spill response should be and a proposal to keep the cap-and-trade provision to utility-only, according to one source familiar with today’s Hill meeting.

Environmental and industry advocates lobbying for energy legislation see the bill as their only chance this Congress.

A Senate aide familiar with the gathering said it is part of Kerry’s regular outreach to the environmental community to ensure it has a voice in the final package that moves forward in the Senate. Kerry has actively courted environmental groups and industry types over the past six months as he has worked to build a coalition of support for the legislation.

Climate change advocates say Kerry’s communication with downtown is evident in how well-received the cap-and-trade provision is among utility companies. The pared-down version under discussion is expected to only cap greenhouse emissions from the utility industry.

So far, companies such as Duke Energy have been supportive of the measure as long as it plans to include the rest of the industry in the future.

You “try to find consensus where you can,” Duke spokesman Tom Williams said. “Our objective is to get going on having the road map. … Right now we’re in a very ambiguous situation from a regulatory standpoint.”

So far, not everyone is optimistic about Senate Majority Leader Harry Reid’s (D-Nev.) chances of getting a bill passed before the August recess.

Former Sen. Bennett Johnston (D-La.), a contract lobbyist for the oil and gas industry, believes there isn’t enough time to get energy legislation done, given the rest of the must-do agenda including the Supreme Court nomination, unemployment benefits and financial reform.

“It’s a question of the clock,” Johnston said. “It’s not a question if something is good legislation; the question is do you have time for it. This is one area where even so-called experts are frequently wrong [because of] a failure to judge the clock,” he added.