Two U.S. business groups opposed on Wednesday the latest version of a climate change proposal circulating in the U.S. Senate, saying it was unfair to power companies and would hurt energy-intensive industries.

Senators John Kerry, a Democrat, and Joe Lieberman, an independent, have crafted a draft bill focusing on capping greenhouse gas pollution from electric power utilities first. It scales back previous ambitions for a broad attack on emissions.

The plan would launch a “cap-and-trade” market in which utilities that cut pollution could sell credits to companies that do not. It expects overall emissions limits would be achieved because the cap on all utilities toughens over time.