DETROIT (AP) — Chrysler LLC said Wednesday that it is closing all 30 of its manufacturing plants for a month starting Friday as it seeks to counter the most severe downturn in U.S. auto sales in more than two decades.

By extending the traditional two-week holiday shutdown period, the struggling Auburn Hills, Mich.-based automaker can adjust production to slowing demand and conserve cash.

In a statement Wednesday, Chrysler said tighter credit markets are keeping would-be buyers away from its showrooms. The company said its dealers are unable to close sales for buyers due to a lack of financing, and estimate that 20 to 25 percent of their volume has been lost due to the credit situation. Sales in November slid 47.1 percent.

Chrysler and larger rival General Motors Corp. have warned they could run out of cash within weeks without financial aid from Washington. Chrysler has said its cash will drop to $2.5 billion by Dec. 31, the minimum needed to meet payroll, pay suppliers and run the company. It would have trouble paying bills after the first of the year.

Operations will be idled at the end of the shift on Friday, Dec. 19. the earliest plants will reopen is Jan. 19, 2009. A few plants will reopen on Jan. 26.

Chrysler operates three transmission plants and a casting plant in Kokomo, Ind., and employs about 5,200 people there. Two of the plants are due to reopen Jan. 19, said United Auto Workers Local 685 President Jeff Shrock.

Some 460 skilled and non-skilled Kokomo employees already were put on indefinite layoff last week.

"The length of this is uncommon. A week before or after, that's not so uncommon. But, the additional weeks are due to the economy. Chrysler dealers, Chrysler Financial, GMAC, all of them are really struggling," Shrock told the Kokomo Tribune.

Chrysler is seeking $7 billion in government loans as it tries to survive the recession and the worst U.S. auto sales slump in 26 years. For the first 11 months of this year, Chrysler sales are down 27.7 percent to 1.4 million vehicles from 1.9 million for the same period last year.

With the U.S. sales slump expected to continue into January, traditionally one of the slowest sales months of the year, the company has little revenue coming in and must pay suppliers $7 billion every 45 days.

In the case of some plants, such as the Toledo Jeep plant in Ohio, operations will resume January 26, but with one less shift. More than 750 workers are being cut on the second shift at the Toledo North plant, said Dan Henneman, United Auto Workers union official for Local 12.

Chrysler's Jeep Liberty, Nitro and Wrangler are assembled at the Ohio plants. Sales of the company's Jeep-brand vehicles fell 41.8 percent in November to 20,302 units.

Henneman said 755 people worked the shift. About 550 workers took a retirement package and 200 will be indefinitely laid off.

General Motors Corp. and Ford Motor Co. have announced extensions of their holiday shutdowns as well.

Chrysler is privately held, with 80.1 percent owned by New York private equity firm Cerberus Capital Management LP.