WASHINGTON (Reuters) - Republican U.S. Senator Susan Collins of Maine said on Wednesday she would oppose Oklahoma Attorney General Scott Pruitt’s nomination to head the Environmental Protection Agency, citing his numerous lawsuits against the agency.

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Pruitt is scheduled to face a Senate confirmation vote on Friday. Unless more Republicans join Collins in opposing Pruitt, his nomination is likely to be approved. Republicans hold 52 of the 100 seats in the chamber and Vice President Mike Pence could cast the deciding vote in case of a tie.

“Due to my concerns about Mr. Pruitt’s commitment to the mission of the EPA, I will cast my vote in opposition to his confirmation,” Collins said in a statement.

President Donald Trump has vowed to cut regulation to revive the oil, gas and coal industries, and has said he can do so without compromising air and water quality.

The Senate Environment and Public Works Committee approved Pruitt’s nomination two weeks ago after Democrats boycotted the vote over concerns about Pruitt’s environmental record.

As Oklahoma attorney general, Pruitt sued the EPA more than a dozen times on behalf of the oil-drilling state and he has cast doubts on the science of climate change.

“His actions leave me with considerable doubts about whether his vision for the EPA is consistent with the agency’s critical mission to protect human health and the environment,” Collins said.

She said Pruitt had sued the EPA on issues of importance to Maine, including mercury controls for coal-fired power plants and efforts to reduce cross-state air pollution and greenhouse gas emissions.

Senator Tom Carper, the top Democrat on the energy committee, and several other Democrats have asked Senate Leader Mitch McConnell to delay a procedural vote on Pruitt scheduled for Thursday.

They want the vote delayed until after the conclusion of an emergency hearing in Oklahoma to be held at 4 p.m. ET that will consider whether emails between Pruitt’s office and officials at oil and gas companies should be released.

Access to those records was requested by the Center for Media and Democracy, a watchdog group, more than two years ago.

Conservative group FreedomWorks blasted Collins, who also voted against the nomination last week of Education Secretary Betsy DeVos. Pence’s vote was needed to break a tie before DeVos was confirmed.

FreedomWorks Chief Executive Adam Brandon said in a statement it was “a shame” that Collins was again aligning herself with “far-left Democrats and special interests.”