This article was updated at 9:52 a.m.

Wyoming Republican Sen. John Barrasso is blocking the confirmation of President Barack Obama's nominee to lead U.S. EPA over concerns about a new White House energy and climate change office headed by former EPA Administrator Carol Browner.

Barrasso quietly objected Tuesday when Senate Democrats tried to fast track Lisa Jackson's nomination to be the new EPA administrator under a unanimous consent request. He remained anonymous until yesterday when he approached Senate Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) with concerns over Browner's appointment, which does not require Senate confirmation.

"The bottom line is Senator Barrasso is concerned about this new structure with an appointed energy czar in the White House with no accountability in the White House," said Barrasso spokesman Gregory Keeley. "Just about how that will operate. He wants to know that. He wants to ensure sufficient transparency and oversight. He wants to be convinced Congress will have the ability to get answers from the appointed czar, Carol Browner. At this stage, he's not convinced that's the case."

Barrasso first raised questions about Browner's role in the Obama administration during Jackson's Senate confirmation hearing earlier this month. "If the two of you disagree on something in terms of an environmental issue, then how does that work between you and the White House?" Barrasso asked.

Jackson replied, "Well, I believe that if I'm confirmed, the EPA administrator is bound by law to uphold the laws that list the EPA administrator as the official to implement them. And so I will take very seriously my legal responsibilities to enact and uphold and implement the laws that Congress puts forward for the American people.

"I'm sure that advisers can agree or disagree on any number of issues," Jackson added. "And her advice and counsel is something I would certainly seek. She has very relevant experience, and she will be dealing across government on many issues with respect to energy and climate change."

White House press officials did not respond to requests for comment about Barrasso's decision to slow down the Jackson confirmation.

According to Keeley, Barrasso asked Boxer to help arrange a meeting with Browner to learn more about the new White House structure. "The bottom line is we're waiting for a meeting to take place," Keeley said, adding that his boss also spoke yesterday by phone with Jackson, the former director of the New Jersey Department of Environmental Protection.

A Boxer aide confirmed that the California Democrat spoke with Barrasso yesterday and referred the request to the Obama White House. The staffer explained that Boxer continues to work to try to win Jackson's confirmation.

Keeley insisted that Barrasso has not put a hold on Jackson's confirmation. Instead, the Wyoming senator only objected to Senate Democratic leadership's bid to move Jackson's confirmation through a unanimous consent request in a brief session a few hours after Obama's inauguration. "He's at no stage objected to a roll call vote," Keeley said.

Barrasso also was concerned about the limited time he had to vet Jackson because the EPA nominee had only returned her written responses to his questions last Friday.

One day into Obama's term, it is little secret that Browner has been promoted to a prominent White House role. The former EPA chief during all eight years under President Bill Clinton participated yesterday in one of Obama's first economic briefings alongside National Economic Director Lawrence Summers, Office of Management and Budget Director Peter Orszag and White House Policy Council Director Melody Barnes.

Senate support for Jackson

For Jackson, New Jersey's Senate delegation is offering the most vocal support. "There is no earthly -- get it? Earthly -- no earthly reason," said Sen. Frank Lautenberg (D-N.J.). "She should not be withheld from an opportunity to go to work."

Sen. George Voinovich (R-Ohio), who sits on the Environment and Public Works Committee, said he, too, backs Jackson.

"From everything I've heard in New Jersey, she's done a pretty darn good job," Voinovich said. "She's tried to the best of her ability to follow the sciences and to throw the ball down the middle. I might argue that maybe it's more to the left than it is to the right, but the main thing is she's trying. She's a very responsible person. And that's the kind of person we need."

Speaking with reporters yesterday, Senate Majority Leader Harry Reid (D-Nev.) took issue with some of the GOP objections so early in Obama's term.

"We're going to move those as quickly as we can," Reid said of the outstanding Obama nominations, which include the EPA administrator, Treasury Secretary nominee Timothy Geithner and Attorney General nominee Eric Holder.

The Senate yesterday did confirm Secretary of State Hillary Rodham Clinton by a 94-2 vote, and Reid said he expected more votes by the end of this week on other nominees. Republicans David Vitter of Louisiana and Jim DeMint of South Carolina voted against Clinton's confirmation.

"We want the Republicans to have input and have the ability to debate these, but if that's not something they're wanting to do -- that is, they're just stalling -- then we're going to have to go through the process of bringing the nomination up and doing cloture," Reid said. "We're going to do that over the weekends, plural, if that's what they want to do."

Though her nomination is in limbo, Jackson has been visible at the start of the Obama administration, attending Tuesday's presidential inauguration and later that night joining Energy Secretary Steven Chu at an environmentally themed ball in Washington. If confirmed, Jackson would be the first African-American head of EPA.

"I only feel like part of a much larger picture," Jackson told the Newark Star-Ledger in her first extended interview published since Obama nominated her for the EPA job. "My symbolism gets lost in his symbolism. His symbolism is extraordinary."

Past EPA administrators have not been among the first presidential appointees to be confirmed. The Senate cleared Christie Todd Whitman, former President George W. Bush's first EPA leader, 11 days after his inauguration. Browner's confirmation came three days after Clinton was sworn in. And President George H.W. Bush's EPA administrator, William Reilly, needed more than two weeks to be confirmed.

Granta Nakayama, a Bush administration appointee, is running EPA pending Jackson's Senate confirmation. Nakayama, 50, has been a noncontroversial figure since joining EPA as its top enforcement official in July 2005.