SAN DIEGO -- Representatives for striking and locked-out grocery clerks promised a "dramatic development" Wednesday in the area's 116-day-old labor dispute over shared costs of medical benefits.

GROCERY STRIKE LOCK OUT VOTE: Cross Picket Line To Shop? DISCUSS: Share Your Thoughts EMAIL ALERT: Sign Up For Grocery Strike Major Development Emails LINKS: UFCW135.com Albertsons.com Safeway.com Vons.com

The announcement -- to be made in Los Angeles, San Diego and Bakersfield -- does not concern Gov. Arnold Schwarzenegger's recent offer to mediate the dispute, said Barbara Maynard of the United Food and Commercial Workers union.

Maynard declined to say what is on tap.

Some 21,000 workers at Safeway-owned Vons and Pavilions stores went on strike on Oct. 11 after contract talks broke down.

The operators of Ralphs and Albertsons markets -- who are in a bargaining agreement with Safeway -- responded by locking out their unionized workers.

One major sticking point has been the demand by the market chains that workers shoulder more of their health care costs.

The workers got a boost Tuesday from two influential unions -- the United Teachers Los Angeles and the Communications Workers of America.

The teachers union urged its members to donate blood to help the community and to show support for the market workers.

A blood drive scheduled between 2:30 p.m. and 8 p.m. outside a Vons on North Alvarado Street in Echo Park is sponsored by the United Food and Commercial Workers union, which represents some 70,000 market workers in Southern and Central California.

"Teachers are taking part in the blood drive because many of our students and their families depend on the county for medical care," said Ted Weber of the UTLA. "The low blood supply is putting our kids in danger."

The union said it also wants to show support for the market workers: "UTLA joins UFCW's commitment to the fight for access to health care," Weber said.

Teachers are expected to begin donating blood at 5 p.m., then join workers on the picket line at the store, according to the teachers union.

Meanwhile, the CWA announced it is donating $100,000 to aid the market workers.

"Their fight is our fight," CWA President Morton Bahr said.

In addition to the $100,000, CWA members and locals have made individual donations to the United Food and Commercial Workers' strike fund, according to the CWA, which represents some 700,000 members nationwide, according to Candice Johnson of the union.