Metalworkers at Brazilian plants of General Motors have voted to go on strike starting Monday in protest against layoffs carried out by the US-based automaker in the country, according to a union that represents them.

The strike for an “indefinite period of time” happens as GM announced it was reducing workforce at its three factories in Sao Paulo state after a drop in sales and exports, a move it dubbed “necessary” for its sustainability.

The Sindmetal union representing metalworkers at the Sao Jose dos Campos plant said workers had voted to enter a strike on Monday, adding that employees of the Sao Caetano do Sul and Mogi das Cruzes plants had also agreed to similar measures.

“The plant will only resume production after the job cuts are canceled and job stability is guaranteed for everyone,” the union said in a statement, arguing that the company had agreed to provide stability for employees until May 2024.

GM employs about 4,000 people in Sao Jose dos Campos, where it makes engines, gearboxes, the Trailblazer SUV and the S-10 truck, according to the union, which said some 1,200 workers previously had their contracts temporarily suspended.

Neither General Motors nor the union detailed how many workers had been laid off.

GM did not immediately comment on the strike but confirmed the layoffs.

“We understand the impact this decision might have on people’s lives, but the move is necessary and will allow the company to maintain the agility of its operations,” GM said in a statement.