March 14 (Bloomberg) -- Toyota Motor Corp.'s Canadian assembly plant faces a vote next week by workers on whether to be represented by the Machinists, the union's first attempt to gain members at an Asian auto plant in North America, an organizer said.

A certification vote for employees of Toyota Motor Manufacturing Canada Inc. in Cambridge, Ontario, is set for March 20, Ian Morland, organizer for the International Association of Machinists' District 140, said in an interview late today. The union filed for a vote for 3,100 of the plant's employees with Ontario's Ministry of Labor yesterday.

``We've filed the necessary paperwork yesterday and the law says a vote must occur within five days,'' Morland said by phone from Cambridge. ``The support we're seeing is overwhelming.

No assembly plant wholly owned by Toyota, Japan's largest automaker, Honda Motor Co., Nissan Motor Co. or Hyundai Motor Co. in the U.S. or Canada, has been organized by the United Auto Workers and Canadian Auto Workers unions. The UAW's past efforts targeting Toyota's Georgetown, Kentucky, plant and Nissan's Smyrna, Tennessee, failed to win enough support.

Calls and e-mails to Toyota officials in Canada and U.S. weren't returned. The Toronto Star reported earlier today the Machinists claimed to have enough support to require a representation vote.

The Machinists began collecting cards from Cambridge workers in November indicating whether they wished to have union support. More than 40 percent of cards turned in were by workers favoring union representation, Morland said.

The Cambridge plant employs 5,059 people and builds Corolla and Matrix small cars, Lexus RX 350 sport-utility vehicles and four-cylinder engines, according to Toyota's Web site.

The UAW represents workers at New United Motor Manufacturing Inc., a joint-venture assembly plant in Fremont, California, that Toyota operates with General Motors Corp.

Toyota's American depositary receipts fell $4.72, or 4.5 percent, to $100.28 today in New York Stock Exchange composite trading.

To contact the reporter on this story: Alan Ohnsman in Los Angeles at aohnsman@bloomberg.net

Last Updated: March 14, 2008 21:12 EDT