Environmentalists are trying to defeat a Senate measure that would bar the Environmental Protection Agency from regulating greenhouse gases.
The Senate is scheduled to vote Wednesday on the Republican-backed plan.
Many businesses support it, saying regulations of heat-trapping gases would drive up their costs and make it harder to hire workers. Environmental groups and many Democrats oppose the measure. They say the government must curb gases that contribute to global warming.
Even if the measure fails, it may resurface in a few days as part of the House-Senate negotiations over government spending.