About 15,000 workers have gone out on strike at 16 Goodyear Tire & Rubber factories across the US and Canada in a dispute over factory closures.
The union says it is unwilling to see more factory closures
The walkout comes after four months of failed contract talks between the tyre-maker and its main union, the United Steelworkers (USW).
USW boss said his members were left with no choice as the company wishes to close two of its North American plants.
Goodyear said it offered a "substantial commitment" to the factories.
The talk of more factory closures comes three years after the USW union agreed to one plant closure and concessions on wages, pensions and healthcare provision.
"We cannot allow additional plant closures after the sacrifices we made three years ago to help this company survive," said USW executive vice-president Ron Hoover.
He added that closing additional factories would devastate communities and threaten Goodyear's long-term viability.
Goodyear said it had to make changes to better compete against cheap foreign imports.
"We simply cannot accept a contract that knowingly creates a competitive disadvantage versus our foreign-owned competition and increases our cost disadvantage versus imports," Goodyear chief negotiator Jim Allen said.
He added that Goodyear, which is continuing with a three-year cost-cutting programme, remained willing to bargain with the union.
The company is the world's third-largest tyre-maker, behind Bridgestone and Michelin, and has a total 100 plants in 29 countries.