NEW YORK — General Motors filed for Chapter 11 bankruptcy protection Monday as part of the Obama administration's plan to shrink the automaker to a sustainable size and give a majority ownership stake to the federal government.

GM's bankruptcy filing is the fourth-largest in U.S. history and the largest for an industrial company. The company said it has $172.81 billion in debt and $82.29 billion in assets.

As it reorganizes, the fallen icon of American industrial might will rely on $30 billion of additional financial assistance from the Treasury Department and $9.5 billion from Canada. That's on top of about $20 billion in taxpayer money GM already has received in the form of low-interest loans.

GM will follow a similar course taken by smaller rival Chrysler LLC, which filed for Chapter 11 protection in April. A judge gave Chrysler approval to sell most of its assets to Italy's Fiat, moving the U.S. automaker closer to a quick exit from court protection, possibly this week.

The plan is for the federal government to take a 60 percent ownership stake in the new GM. The Canadian government would take 12.5 percent, with the United Auto Workers getting a 17.5 percent share and unsecured bondholders receiving 10 percent. Existing GM shareholders are expected to be wiped out.

Albert Koch, who helped Kmart Corp. through its Chapter 11 reorganization, will serve as GM's chief restructuring officer.

Administration officials, speaking on condition of anonymity in advance of Obama's public remarks, said they expect the bankruptcy court process to last 60 to 90 days. If successful, GM will emerge as a leaner company with a smaller work force, fewer plants and a trimmed dealership network.

President Barack Obama is scheduled to address the nation about GM's future at midday from Washington, and GM CEO Fritz Henderson is to follow him with a news conference in New York.

GM also revealed Monday that it will permanently close nine more plants and idle three others.

The Pontiac, Mich., and Wilmington, Del., assembly plants will close this year, while plants in Spring Hill, Tenn., and Orion, Mich., will shut down production but remain on standby. One of the idled plants will be retooled to build a small car.

Seven powertrain and parts stamping plants will be closed starting in June 2010, while one stamping plant will be idled in a standby capacity.

GM's filing comes 32 days after a Chapter 11 filing by Chrysler, which also was hobbled by plunging sales of cars and trucks as the worst recession since the Great Depression intensified.