By Bernie Woodall

DETROIT (Reuters) -- The United Auto Workers union won its first organizing vote on Friday at a foreign-owned auto assembly plant in the U.S. South, in a groundbreaking victory after decades of failed attempts.

About 71 percent of skilled trades workers who cast ballots at Volkswagen AG's (VOWG_p.DE) factory in Chattanooga, Tennessee voted to join the UAW, according to the company and the union.

The skilled trades workers account for about 11 percent of the 1,450 hourly employees at the plant.

If the UAW victory, as expected, survives an appeal by Volkswagen to the National Labor Relations Board, the 164 skilled trades workers will be the first foreign-owned auto assembly plant workers to gain collective bargaining rights in the southern United States.

While the unit of skilled trades workers who maintain the assembly machinery are a fraction of the hourly work force, observers said a victory is a significant and could serve as a launching pad for the union’s efforts to organize other foreign-owned plants in the South.

“It gives the UAW a significant new tool in trying to organize the foreign automakers in the South. Symbolically, it’s going to be huge,” said Dennis Cuneo, a former automotive executive who has engaged the UAW in past organizing campaigns.

Gary Casteel, UAW secretary-treasurer and head of the union's organizing efforts, downplayed the significance of the vote and its influence on the UAW's attempts to organize workers at Southern plants including those owned by Nissan Motor Co (7201.T) and Daimler AG's (DAIGn.DE) Mercedes-Benz.

“To the overall grand plan of the UAW it’s probably not monumental, but to those workers, it’s a big deal,” Casteel said in an interview on Friday.

Casteel, and Chattanooga UAW Local 42 President Mike Cantrell, in a separate interview on Thursday, said election in Chattanooga was a result of the "frustration" of skilled trades workers there of not having collective bargaining for wages and benefits.

"Every case has to be built on the circumstances" at each plant, Casteel said. "We are not filing on Nissan or Mercedes tomorrow, but if our evaluation proved that there was a unit that was ready and strong enough to have an election, certainly we would explore it."

The union narrowly lost a February 2014 ballot in which all of the Chattanooga plant’s hourly workers were eligible to vote.

During that vote, Republican U.S. Senator Bob Corker, whose hometown is Chattanooga, said, “I’ve had conversations today and based on those am assured that should the workers vote against the UAW, Volkswagen will announce in the coming weeks that it will manufacture its new mid-size SUV here in Chattanooga."

The UAW’s current president, Dennis Williams, and its president in 2014, Bob King, said Corker's comment as well as “interference” from anti-union groups including one led by small government advocate Grover Norquist, tainted the election.

Since then, VW has announced to build the midsized SUV at Chattanooga, and it plans to gradually add as many as 2,000 plant workers for production that will ramp up from its December 2016 start.

Casteel said the UAW maintains a narrow majority of support among VW Chattanooga hourly workers, but it is not pursuing a vote by all hourly workers because of concern of “facing the same outside pressure that we faced last time.”

VW officials have publicly declined to say that its relationship with the UAW has soured since 2014 when it was clearly the most open to the union among foreign automakers in the South. It has appealed the decision by an NLRB regional official to allow election in Chattanooga only because it wants all of the plant’s hourly workforce included in any labor representation vote.

Plus, VW said that the timing of the vote was bad, considering its ongoing scandal over diesel emissions.

Casteel and Cantrell pointed out that the UAW filed for the vote in August, more than a month before VW's emissions scandal came to light in mid-September.

The UAW has used its relationship with the German union IG Metall as a way to get into the Chattanooga plant. IG Metall represents VW workers and is influential in corporate decisions due to its membership on VW corporate governing boards.

Since the February 2014 vote, VW has established worker representation groups that include UAW members as well as members of an anti-UAW group. Both groups have access to plant managers to discuss work issues but not wage or benefit issues. The UAW has more access to plant managers than the anti-UAW group called American Council of Employees because it has proven to have a greater measure of support.

(Reporting by Bernie Woodall; Editing by Bernard Orr and Tom Brown)