WASHINGTON: Workers at Volkswagen's Chattanooga plant in the US state of Tennessee have voted overwhelmingly to unionise at the third attempt, the company and the United Auto Workers (UAW) have announced.

The ballot, which ended on Friday, saw 73 per cent of the workers backing the move. The result has yet to be confirmed by the National Labor Relations Board, an agency of the United States federal government.

The UAW, which is seeking to expand its presence in the US automotive sector, sees the outcome as a significant victory.

Two attempts to unionise the plant over recent years failed. But the union has scored major successes recently. In the autumn, it secured better conditions and a pay rise of around 25 per cent at the main US automotive companies, General Motors, Ford and Stellantis (formerly Chrylser), following a lengthy strike.

Until now, the union has had little success in the southern states and the plants of non-US vehicle makers. It has also failed to unionize Tesla workers.

A total of 3,613 workers, equivalent to 83.5 per cent of the labour force, cast their ballots, with 2,628 voting to be represented by the UAW.

Germany's powerful IG Metall union said on Saturday that Chattanooga was the VW brand's sole plant without union representation. Daniela Cavallo, head of the VW works council, said the Chattanooga workers had "rewritten US trade union history."