NASHVILLE -- The United Auto Workers dropped its appeal of a worker vote against unionizing at a Volkswagen plant in Tennessee, a move that the union said should put pressure on Republican politicians to quickly approve incentives the German automaker is seeking to expand its lone U.S. assembly plant.

The prolonged fight over labour issues at the Chattanooga facility appeared headed for a lengthy National Labor Relations Board appeal until the UAW announced an hour before a scheduled hearing that it was ending its challenge. The February vote went against the union 712-626.

Some GOP lawmakers had blamed the appeal for holding up expansion plans at the plant -- and the UAW says that perceived obstacle is now out of the way.

"Now they need to step up and do what's right for VW and those workers over there, get the incentives without any strings attached," UAW Regional Director Gary Casteel said in a phone interview.

The appeal had focused on public statements from U.S. Sen. Bob Corker, Tennessee Gov. Bill Haslam and other GOP officials that the union argued raised fears among workers about the plant's future if they voted to organize.

Union supporters also chafed at revelations that a previous $300 million incentive package from Tennessee had been made contingent on the labour situation there concluding to the satisfaction of the state, where anti-UAW Republicans hold a vast majority.

The UAW says it will now focus on a congressional investigation launched by two House Democrats into the anti-unionization campaign, though it's unclear what that probe will achieve unless it is also taken up by the Democratic-controlled Senate.

Volkswagen wants to introduce a German-style works council at the plant to represent both salaried and blue-collar workers, but the company's interpretation of U.S. law has been that it can't do so without the involvement of an independent union.

The company issued a statement welcoming the UAW decision as "an important gesture for a constructive dialogue in Chattanooga." Volkswagen said it will continue to pursue its efforts to establish "a new, innovative form of co-determination in the USA."

Half of Volkswagen's 20-member supervisory board is made up of worker representatives, including the head of the company's Global Group Works Council . The organization that represents works councils at VW plants around the world called on Tennessee officials to "create conditions that provide Volkswagen with the economic basis for safeguarding existing jobs in Chattanooga over the long term and for creating new ones."

"The UAW has taken the first step and all those responsible in the USA must now look to the future and pull in the same direction," the Works Council statement said.

Corker and Haslam oppose UAW expanding its reach in Tennessee, arguing that a union win at Volkswagen would hurt the state's ability to attract other manufacturers and suppliers. The vote proved a setback for the UAW, which hopes to expand to foreign-owned auto plants in the U.S., particularly those in the South.

Haslam told reporters on Monday that he was eager to resume negotiations with Volkswagen for the first time since January.

The governor said that the timing of any incentive package would be linked to the company's plans for the plant, and that it was unclear whether the state Legislature would have to be called back into session to approve the subsidies.

Haslam also acknowledged that the end of the NLRB case does not preclude future union involvement in the plant.

"Obviously at any point in time, if there's an election if the UAW wins, they win," Haslam said. "Our concern here was there was a clear election and they hadn't won."

Corker, a former Chattanooga mayor, was particularly vocal during the three-day union vote in February, predicting the company would announce an expansion within two weeks of workers rejecting the union.

The senator later blamed the UAW appeal -- and the resulting delay in certifying the results of the union election -- for putting a hold on expansion talks at the plant. Corker and Haslam both fought the union's efforts to compel them to produce documents and appear at NLRB hearings as part of the appeal.

"It's a shame the UAW slowed the momentum on our expansion conversations with Volkswagen, but now it's time for VW, our state and our community to re-engage and move forward with bringing additional jobs to Chattanooga," Corker said in a statement.