WASHINGTON – Senate Democrats on Wednesday defeated a Republican effort to ban the Environmental Protection Agency from controlling gases blamed for global warming.

In a 50-50 vote, the Senate rejected the measure by Minority Leader Mitch McConnell of Kentucky and Sen. James Inhofe of Oklahoma that would have repealed a 2009 finding by federal scientists that climate change caused by greenhouse gases endangers human health.

Passage would have prevented the agency from using existing law to regulate heat-trapping pollution. The amendment — to a small-business bill — needed 60 votes to pass.

Maine’s Republican senators split their votes. Olympia Snowe voted for the measure while Susan Collins voted against it.

Snowe says scientific evidence shows “we must address climate change.” But giving the EPA such authority “will only exacerbate economic uncertainty for manufacturing facilities, including 71 in Maine,” Snowe said.

Collins said the McConnell measure went too far, adding that the EPA should not regulate greenhouse gas emissions without legislative direction of the type she proposed last year with Democratic Sen. Maria Cantwell of Washington. That proposal, she said, “would have reduced carbon pollution while protecting families from energy price increases.”

Collins and Snowe split again on a failed proposal by Democratic Sen. Jay Rockefeller of West Virginia, that would have forced the EPA to delay for two years any regulation of greenhouse gas emissions.

Collins said she “supported the Rockefeller amendment . . . to allow time for Congress to act in a responsible way.”