(Corrects spelling to Senator Roy Blunt, not Blount, paragraph 10)
By Valerie Volcovici
WASHINGTON, June 27 (Reuters) - President Barack Obama made a plea this week for the U.S. Senate to confirm his choice to head the agency that will oversee the core of his new climate change plan, but nominee Gina McCarthy's prospects seem increasingly in doubt.
McCarthy was nominated by Obama in March to lead the U.S. Environmental Protection Agency where she is currently the top air quality official.
She has yet to receive a vote in the full U.S. Senate after narrowly being approved by the Senate Committee for the Environment and Public Works on a party-line vote.
In his speech Tuesday laying out a climate action plan, Obama said McCarthy was well qualified for the job and has bipartisan credentials. The Senate should confirm her "without any further obstruction or delay," Obama said.
McCarthy has worked for several Republican governors, including 2012 presidential candidate Mitt Romney when he was governor of Massachusetts. She was seen by many as a choice that could work with lawmakers from both parties.
But many Republicans are bitterly against proposed new regulations from the EPA on coal-fired power plants and could seek to block McCarthy's confirmation.
"Sad to say, but I think (Obama) may have effectively sacrificed her confirmation," said Manik Roy, vice president for strategic outreach for the Center for Climate and Energy Solutions.
McCarthy has received public support from industry representatives and environmental groups alike for her ability to navigate political divisions.
Roy and other analysts have said opposition to her confirmation has less to do with her and more to do with ideological opposition to regulation.
Republican Senator Roy Blunt maintains a hold on her nomination over a river project in his state, while members of the Senate environmental committee continue to press McCarthy and the EPA over the transparency of the agency's emails and the economic analysis that goes into its rulemaking.
Reaction by some Senate Republicans to Obama's climate plan signal a tough fight for McCarthy.
Republican Senator John Barrasso said regulations targeting coal-powered plants will strangle the economy. And he suggested McCarthy had lied when asked at her confirmation hearing in April about the agency's plans to regulate existing power plants.
"The agency is not currently developing any existing source greenhouse gas regulations for power plants," McCarthy told the panel.
Speaking on the Senate floor, Barrasso said, "She has recently reported to the Senate that the things the president is talking about today are things she has known nothing about. So either she was ignorant about what's going on at EPA, a place where she's been an assistant director for the last four years, or she is arrogant.
"Either way, I think this tarnishes her chances of being approved by the Senate, tarnishes her nomination."
Senator Barbara Boxer, the Democrat who chairs the environment panel, told reporters last week that she will lead a public campaign for McCarthy.
Roy said that even if the current acting administrator, Bob Perciasepe, stays on in his role, McCarthy will be able to take the lead on Obama's climate agenda.
Allison Macfarlane, another member of Obama's energy team, was confirmed by the Senate on Thursday to a full term as chairwoman of the U.S. Nuclear Regulatory Commission, which she has led since July 2012. (Additional reporting by Douwe Miedema, Editing by Ros Krasny and Eric Walsh)