WASHINGTON (Reuters) - Republican U.S. Senator Susan Collins said on Wednesday she will oppose Andrew Wheeler, President Donald Trump’s pick to head the Environmental Protection Agency, complicating the nominee’s path to approval by the Senate.

FILE PHOTO: U.S. Environmental Protection Agency (EPA) Acting Administrator Andrew Wheeler addresses staff at EPA headquarters in Washington, U.S., July 11, 2018. REUTERS/Ting Shen

Collins said Wheeler’s efforts to roll back standards on emissions blamed for climate change takes the country in the wrong direction.

Trump’s pick, a former lobbyist for coal and other energy interests, also faces a backlash from other Republican lawmakers over his support of policies favorable to the ethanol industry. This could make it harder for him to win the majority of votes required for approval in the 100-member, Republican-led chamber.

Senate Majority Leader Mitch McConnell has scheduled the confirmation vote for Wheeler for Thursday at 12:30 p.m. EST (1730 GMT).

Five Republican senators from oil states, led by Ted Cruz of Texas, sent a letter to Wheeler dated Feb. 11 asking about his biofuels policies, and saying their confirmation votes could hinge on his responses.

The Senate voted 53-45 in a procedural measure on Wednesday to end debate on Wheeler’s nomination. Collins supported that measure but will vote against his nomination.

A bipartisan group of senators has also pressured Wheeler to take stronger actions to control a group of toxic chemicals found in some U.S. drinking water known as PFAS, used in Teflon and firefighting foam. Wheeler said this month the EPA plans to take actions on the pollutants but stopped short of setting limits until later this year.

The EPA declined to comment. The White House did not immediately respond to a request for comment.

Wheeler has been running the EPA since his predecessor Scott Pruitt resigned in July under a cloud of ethics controversies. Collins said Wheeler is qualified for the job and acts in accordance with ethical standards.

“However, the policies he has supported as Acting Administrator are not in the best interest of our environment and public health, particularly given the threat of climate change to our nation,” said Collins, who voted for Wheeler last April in his confirmation for EPA deputy. Collins added that her state of Maine is at the receiving end of pollution generated by coal-fired power plants in other states.

Collins had also voted against Pruitt’s confirmation.

Since becoming acting administrator, Wheeler has overseen proposals to roll back the Obama-era Clean Power Plan on carbon emissions from power plants, limits on mercury emissions from coal plants, and standards on carbon dioxide emissions from cars and trucks.

Senator Joe Manchin, a conservative Democrat, who also voted last year to confirm Wheeler as EPA deputy, voted against him in Wednesday’s procedural vote. Wheeler “hasn’t demonstrated a desire or a will to make any meaningful progress on clean drinking water standards and has rolled back clean air standards,” he said.

Manchin, of coal producing West Virginia, said the EPA’s proposed changes to the mercury rule “will only serve to further undermine the status of our coal-based utilities.”

Many U.S. utilities had already planned adjustments to their coal-burning generators to comply with the tighter mercury standards, and the utilities are worried that proposals for looser rules could lead to regulatory uncertainty.