Unionized workers have gone on strike at some Chrysler plants in the United States, after negotiators failed to agree on a new contract before a union-imposed deadline.

Some plants continued working after the deadline Wednesday, but workers set up picket lines outside several Chrysler factories in Michigan.

Last month, union employees staged a two-day strike at the largest U.S. automaker, General Motors. The contract agreement the union reached with G.M. was to be used as a template for contracts with Chrysler and Ford.

The General Motors deal included creation of a company-funded, union-run trust fund for retiree health care.

U.S. auto companies have been trying to cut costs so they can better compete with Asian automakers who have been taking a larger share of the car buying market.

Some information for this report was provided by AFP, AP and Reuters.