UPDATE 1-UAW urges push to save Toyota plant in California

* UAW urges drive to save Toyota plant in California

* Lawmakers, Schwarzenegger call on Japanese automaker (Adds detail on Schwarzenegger)

DETROIT, July 27 (Reuters) - The United Auto Workers union on Monday urged its members to contact U.S. lawmakers to try to convince Toyota Motor Corp (7203.T) to keep operating a California assembly plant that could be targeted for closure.

In an email to members, retirees and supporters sent on Monday, the union said it would call on members of Congress to ask Toyota to keep the San Francisco-area plant in operation in order to save 4,500 union-represented jobs.

"We believe that Toyotas sold in the United States should be made in the United States. California is by far Toyota's single biggest market for car sales in the United States," the UAW said in its email message.

The UAW represents workers at the Fremont, California assembly plant that Toyota has operated with General Motors for the past 25 years as a joint venture.

The union's lobbying effort represents a broadening in the debate over the future of the plant that began when GM decided to drop its share of the pioneering joint venture as part of its U.S.-government sponsored bankruptcy.

A Toyota spokesman was not immediately available for comment.

Toyota said last week it would begin negotiations with Motors Liquidation Co MTLQQ.PK, the entity that has taken over management of GM assets left in bankruptcy, including the U.S. automaker's stake in the plant.

The plant, commonly known by its acronym NUMMI for the New United Motor Manufacturing Inc, has operated as a 50-50 partnership by GM and Toyota since 1984.

The UAW said it wanted U.S. lawmakers to intervene to "mandate fair bargaining" between Motors Liquidation and Toyota on the future of the plant.

NUMMI is the only auto assembly plant in California.

Last week, 17 members of California's congressional delegation, including Sen. Dianne Feinstein and Sen. Barbara Boxer, sent an open letter to Toyota President Akio Toyoda urging him to keep the plant open.

California Gov. Arnold Schwarzenegger has also formed a team of officials to try to save the plant and its jobs and sent a state representative to meet with Toyota in Japan.

GM threw the future of the plant into question late last month when it opted to leave its share of the joint-venture in bankruptcy under its U.S.-government guided restructuring.

The U.S. automaker had previously announced a plan to stop production of the Pontiac Vibe -- the only GM vehicle built at the plant -- in August.

Like other major automakers, Toyota has been hit hard by the downturn in U.S. auto sales and has had to scale back production at its existing plants and freeze construction of a planned facility in Mississippi.

The Japanese automaker's senior U.S. representative, Yoshi Inaba, said last week that Toyota plans to increase the share of its U.S. auto sales that are built in North America from near 60 percent.

But Inaba said it was also unlikely that Toyota would opt to buy GM's 50-percent share of NUMMI out of bankruptcy.

Toyota has said a final decision on the fate of NUMMI will take time to reach because of the complexity of the talks. (Reporting by Kevin Krolicki; editing by Carol Bishopric)