Allbaleun, a labor collective representing younger Seoul Metro employees, will strike alongside the subway operator's largest union on December 12.

The union announced during a news conference in front of City Hall that it would launch a general strike if Seoul continued to neglect workers' demands, which it characterized as based in rationality and common sense.

The Seoul Transit Corporation Labor Union, the largest body representing the Seoul Metro, had announced its own planned strike on Tuesday, saying wage cuts were becoming a real prospect.

The subway operator has been negotiating separately with the three unions, each of whose members authorized a strike after labor commission mediations were suspended.

Allbaleun's members urged the operator of Seoul Subway Lines 1 to 8 to compensate extra time worked on the city's policy projects separately rather than folding the hours into annual wage increases.

They also demanded new hires, stating that retirements have left their workforce one-thousand members short, but Seoul Metro only plans to employ 200 more.