NASHVILLE (AP) - The National Labor Relations Board on Wednesday declined to take up Volkswagen's challenge of a union vote at its lone U.S. assembly plant in Tennessee.

In a 2-1 decision, the panel refused to consider the German automaker's appeal on the basis that it raised "no substantial issues warranting review."

Volkswagen had unsuccessfully sought to block a union vote among a group of about 160 workers specializing in the repair and maintenance of machinery and robots, arguing that labor decisions should be made by all 1,400 blue-collar workers at the plant. The company also questioned the timing of the vote amid its struggles to cope with the fallout of its diesel emissions cheating scandal.

The NLRB's regional director allowed the vote to move forward and the United Auto Workers won the December election on a 108-44 vote, ending a decades-long losing streak in union elections among foreign automakers in the South.

But Volkswagen declined to enter into contract negotiations while challenging the election to the federal labor panel.

"With today's order, the NLRB has clearly stated that it views the skilled-trades election in Chattanooga as a legal and appropriate step toward meaningful employee representation," UAW Secretary-Treasurer Gary Casteel said in a statement.

"We call on Volkswagen to immediately move forward with UAW Local 42, in the German spirit of co-determination," he said.

Volkswagen spokesman Scott Wilson said in an email that the company is "reviewing the decision and evaluating our options."

The effort to unionize only a small portion of workers at the plant followed a narrow UAW defeat in a 2014 union vote among all hourly workers. In the run-up to that vote, state lawmakers warned that state tax credits could be threatened if the union won the election.

Anti-labor groups rented billboards around Chattanooga linking Detroit's woes to UAW succe ss there, and Republican U.S. Sen. Bob Corker proclaimed that Volkswagen would quickly announce a decision to build a new SUV at the plant if the union was defeated.

While Volkswagen publicly denied that there was a link between the union vote and the plant expansion decision, union supporters argued that the GOP officials' statements had a chilling effect on workers who worried about the plant's future if the new vehicle wasn't produced there.

As it turned out, Volkswagen announced the new SUV would be produced in Chattanooga five months after the vote. The plant is scheduled to begin producing the new vehicle before the end of the year.

Tennessee Gov. Bill Haslam on Wednesday said that he had agreed with Volkswagen's challenge, and that the UAW's effort to make the unionization push at the plant during the emissions scandal "shows a lack of respect for the overall health and wellbeing of the company."