Detroit ? General Motors Corp. Chairman and CEO Rick Wagoner will step down immediately at the request of the White House, and new directors will make up the majority of GM’s board in a major management shake-up of the country’s largest automaker, GM confirmed today.

The sweeping changes come just hours before President Barack Obama plans to unveil additional restructuring efforts designed to save GM and perhaps its Detroit-area competitor, Chrysler LLC, both of which are living on $17.4 billion in government loans and have requested $21.6 billion more.

GM President and Chief Operating Officer Fritz Henderson will take over as CEO, the company said in a statement released just after midnight.

Board member Kent Kresa, a former chairman and CEO of Northrop Grumman Corp., was named interim chairman. He said the board has known for some time that restructuring would bring a change in stockholders and create a need for new directors with additional skills.

The directors who will be replaced have not been determined, but the change will take place at the company’s annual meeting in Detroit in August, Kreska said in a written statement.

Two people familiar with Obama’s plan said Sunday that the administration would give GM enough aid to restructure over the next 60 days, while Chrysler will get up to $6 billion and 30 days to complete an alliance with Italian automaker Fiat SpA. The officials spoke on condition of anonymity because they were not authorized to make details public.

The administration, the people said, found that neither company could be viable under restructuring plans submitted to the government, so more steps would be required. Despite finding that Chrysler could not survive without a partner, the administration did not demand a change in the Auburn Hills, Mich.-based company’s management.

Chrysler has been led by former Home Depot CEO Robert Nardelli since August 2007.

Wagoner, 56, has repeatedly said he believed it was better for him to lead GM through its crisis, but he has faced sharp criticism on Capitol Hill for what many lawmakers regard as years of missteps, mistakes and arrogance by the Big Three automakers.

Wagoner joined GM in 1977, serving in several capacities in the U.S., Brazil and Europe. He became president and chief executive in 2000 and has served as chairman and CEO since May 2003.

Wagoner, in an interview with The Associated Press in December, declined to speculate on suggestions from some members of Congress that GM’s leadership team should step down as part of any rescue package.

“I’m doing what I do because it adds a lot of value to the company,” Wagoner said in a Dec. 4 interview as GM sought federal aid from the Bush administration. “It’s not clear to me that experience in this industry should be viewed as a negative, but I’m going to do what’s right for the company and I’ll do it in consultation with the (GM) board (of directors).”

Auto industry analysts credit Wagoner with doing more to restructure the giant automaker than any other executive. But given that he has been at GM’s helm for so long, many of his critics say he moved too slowly to take on the United Auto Workers and shrink the company as its market share tumbled.

“Given the history, a change in management could hardly hurt and might do some good,” Sen. Charles Schumer, D-N.Y., said Sunday.

Among his biggest accomplishments as CEO, Wagoner presided over a landmark contract agreement with the UAW in 2007. In that four-year agreement, the automaker successfully transferred nearly $50 billion in health care liabilities to the union as it sought to reduce labor costs, especially huge liabilities to retirees.

In 2004, Wagoner sought to reduce GM’s brands by shutting down the Oldsmobile line of cars — a costly project because it required huge payouts to dealers. He has also reduced the company’s workforce by tens of thousands and closed factories around the country.