DETROIT (AP) - General Motors Corp. said it will cut 21,000 U.S. factory jobs by next year, phase out its storied Pontiac brand and ask the government to take company stock in exchange for half GM's government debt as part of a major restructuring effort needed to get more government aid.

The struggling automaker also said it will offer 225 shares of common stock for every $1,000 in notes held by bondholders as part of a debt-for-equity swap.

The announcements came in a filing Monday with the Securities and Exchange Commission.

GM is living on $15.4 billion in government loans and faces a June 1 deadline to restructure and get more government money. If the restructuring doesn't satisfy the government, the company could go into bankruptcy protection.

GM said in a news release that it will ask the government to take 50 percent of its common stock in exchange for canceling half the government loans to the company as of June 1.

GM said the bond exchange aims to wipe away a large majority of the company's $27 billion in unsecured debt. The company estimates that after the exchange, bondholders would own 10 percent of the company.

In addition, GM is offering the United Auto Workers stock for at least 50 percent of the $20 billion the company must pay into a union run trust that will take over retiree health care expenses starting next year.

All the stock offerings mean that current common stockholders would own only 1 percent of the company under the deals, the press release says.

In premarket trading, GM shares rose 7 cents, or 4.1 percent, to $1.76.

GM said it would speed up six additional factory closings that were announced in February, although it did not identify them in its news release. Additional salaried jobs cuts also are coming, beyond the 3,400 in the U.S. completed last week.

Including previously announced plant closures, the restructuring will leave GM with 34 factories at the end of next year, down from 47 at the end of 2008.

The company also said it plans to thin its dealership ranks by 42 percent from 2008 to 2010, cutting them from 6,246 to 3,605.

"The Viability Plan reflects the direction of President Obama and the U.S. Treasury that GM should go further and faster on our restructuring," GM CEO Fritz Henderson said in a statement. "This stronger, leaner business model will enable GM to keep doing what it does best - provide great new cars, trucks and crossovers to our customers, and continue to develop new advanced propulsion technologies that are vital for our country's economy and environment."

The new plan lowers GM's break-even point in North America to an annual U.S. sales volume of 10 million vehicles, the company said. That's slightly more than the current sales rate, and most economists expect an uptick in the second half of the year.

"This lower break-even point better positions GM to generate positive cash flow and earn an adequate return on capital over the course of a normal business cycle, a requirement set forth by the U.S. Treasury," the statement said.

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