Ssangyong Motor on Sunday decided to lock out striking workers at company headquarters in Pyeongtaek, but with no signs of the carmaker's union backing down, a physical confrontation looms.

Earlier in the day, the automaker reported its lockout plan to the National Labor Relations Commission and the Pyeongtaek Municipal Government. It said if unionized workers do not voluntarily leave the factory, it will sue the union for obstruction of business and request police assistance.

Facing a massive layoff at the ailing SUV maker, the union started a general strike on April 21 for an unlimited period. It broke into headquarters and took over the office the next day.