It’s a make-or-break week for environmental advocates and senators struggling to keep climate change provisions in the mix during a pre-recess energy debate.

Senate Majority Leader Harry Reid is sticking with his plan to start debate on an energy bill July 26, a deadline that means he must quickly produce legislation — and that increases pressure on supporters of adding carbon dioxide controls to the measure.

“At this point in the calendar, time is a big constraint on action,” said Daniel J. Weiss, a climate expert at the liberal Center for American Progress, who last week listed provisions from existing energy and climate bills that could be compiled into one measure.

Reid, D-Nev., said July 13 that the bill would address the Gulf of Mexico oil spill, “clean” energy and job creation and will include a tax title and language on pollution from power plants. That last provision is widely seen as a limit on greenhouse gases, although Reid carefully avoided using the word “cap” or other politically charged nomenclature that Republicans have tagged as “energy taxes.”

The effort got a boost when all 12 freshman Democratic senators called for the inclusion of carbon pricing in the energy bill.

While Reid’s words and the freshmen’s support have helped revive efforts to add climate provisions to the bill, it remains an uphill fight.

John Kerry , D-Mass., and Joseph I. Lieberman , I-Conn., spent months negotiating with industry and environmentalists on an economy-wide climate bill, only to scale back their efforts in a bid to win 60 votes. They are now trying to broker an agreement between electric utilities and major environmental groups on a cap covering emissions from power plants.

Those talks have stumbled over the familiar dispute about the distribution of emission allowances, as well as new demands by utilities for exemptions from EPA regulations on traditional pollutants, including lead, mercury and ozone, in exchange for agreeing to carbon dioxide limits, lobbyists said. In a July 14 letter to senators, major health and environmental groups called such exemptions “simply unacceptable” and a threat to millions of lives.

Further complicating matters, some manufacturing groups — American Chemistry Council and the National Rural Electric Cooperative Association — have come out in opposition to the idea of a utilities-only cap.