The United Auto Workers (search) union gave no details Monday of its new four-year labor contract agreement with the Chrysler arm of DaimlerChrysler (DCX).

The union said it was still negotiating with General Motors Corp. (GM) and Ford Motor Co. (F) after a self-imposed midnight Sunday deadline came and went.

Here is some key background on the automakers, the union, and the issues in the negotiations:

Detroit's Big Three automakers — GM, Ford and Chrysler — face falling market share, escalating incentives to get consumer to buy vehicles, shrinking profits, and mounting health care and pension costs.

In August, Toyota Motor Corp. outsold Chrysler in the United States for the first time. The combined U.S. market share of the Big Three automakers plunged to a record low of 57.9 percent in August, down from about 74 percent just 10 years ago, according to Autodata. At least one Wall Street analyst has said that one of the U.S. automakers could go bankrupt by the end of the decade.

The Issues

— Closing plants: Ford, which lost a total of $6.43 billion over the past two years, has said it wants to close four plants in the United States. The current contract restricts automakers from closing facilities.

Chrysler, which lost $1.1 billion in the second quarter due to Detroit's price war, has the highest production costs of the Big Three automakers, and wants to sell or close several of its unionized parts companies.

GM has two aging vehicle assembly plants on the East Coast that analysts say the automaker would like to close.

— Health care/pensions: GM is burdened by its "legacy costs," the heavy expense of supporting the pension and health care benefits of 1.2 million current employees, retirees and their dependents. The world's largest automaker is also the biggest private provider of health care, with $4.5 billion spent on health care last year.

The United Auto Workers (UAW) union has said it will resist efforts to shift escalating health care costs onto workers.

The Big Three automakers have a combined deficit of roughly $31 billion in their U.S. pension plans, a hefty burden to carry. Foreign automakers have a younger work force and virtually no retirees from their North American plants.

— Expand the union: The UAW has said its top priority is to unionize more plants, including parts suppliers and DaimlerChrysler's Mercedes plant in Alabama.

Earlier this year, the UAW expanded in the southern United States, a region regarded as unfriendly to unions, by organizing more than 4,000 workers at five facilities run by DaimlerChrysler's Freightliner heavy truck operations. The UAW has also won the right to organize at auto parts suppliers Dana Corp. and Johnson Controls Inc.

The Union

— The International Union, United Automobile, Aerospace and Agricultural Implement Workers of America (UAW) represents about 676,000 active workers, roughly half of which work in the auto industry, and over 500,000 retired members. Total UAW membership, which also includes workers outside the auto industry, has dropped to about 676,000 from a high of 1.5 million in 1979.

— The current four-year contract covers 291,510 workers at GM, Ford, Chrysler and the auto parts suppliers Delphi Corp. and Visteon Corp. The active members include 117,780 at GM, 72,570 at Ford, 60,170 at DaimlerChrysler, 30,100 at Delphi and 21,880 at Visteon.

— The head of UAW, Ron Gettelfinger (search), 59, is leading the union for the first time in national contract talks with the automakers. Prior to becoming UAW president last year, Gettelfinger guided the Ford department of the UAW.

— The last major UAW strike against a Big Three automaker was a 59-day walkout at two General Motors' parts plants in Flint, Michigan in the summer of 1998. GM vehicle sales plummeted that summer, and the automaker still hasn't recovered its pre-strike market share.