WASHINGTON (Reuters) - The Obama administration has added Wall Street expertise to its team overseeing the restructuring of General Motors and Chrysler, naming Steven Rattner as adviser to Treasury Secretary Timothy Geithner.

Rattner, co-founder of private equity firm Quadrangle Group LLC, will advise Geithner on a variety of economic and financial matters and will lead Treasury's efforts on the automobile sector, the White House said on Monday.

Rattner had been a leading contender to become car czar, but President Barack Obama surprised industry analysts and executives by opting against a single-appointee to handle the politically tricky task of overhauling Detroit.

Instead, Obama has settled on a panel led by Geithner and White House economic adviser Larry Summers that also includes representatives from the Labor, Transportation, Energy and Commerce departments and the Environmental Protection agency.

Ron Bloom, a restructuring expert with investment banking experience, has also joined Treasury to work on the auto issue. But Bloom's chief expertise is advising labor unions on restructuring, especially in the steel industry.

Rattner, a Democratic fund-raiser who is married to a former finance powerhouse for the party, has stepped down from Quadrangle, which he co-founded in 2000.

Previously, he had been a managing director at investment bank Lazard Freres & Co, where he was a member of the media team. Before that, he was a journalist with the New York Times.

The task force is charged with overseeing the government bailout of GM and Chrysler and deciding whether to provide more aid to the cash-strapped automakers.

The companies, which were promised $17.4 billion in government loans in December, requested nearly $22 billion in additional aid last week when they submitted new restructuring plans.

The task force held its first meeting on Friday, and Geithner told panel members to present restructuring recommendations at the next meeting.

The Treasury has also retained law firms with bankruptcy experience -- Cadwalader, Wickersham & Taft and Sonnenschein, Nath & Rosenthal -- and investment bank Rothschild.

Outside advisers to the Treasury are exploring financing options with private lenders, a Treasury official said.

(Reporting by Kevin Krolicki and John Crawley; Editing by Matthew Lewis, Brian Moss and Ted Kerr)