Unionized workers of Seoul Metro, which operates subway Line Nos. 1 through 8, hold placards calling for better working conditions as they take part in a press conference in front of the City Hall in central Seoul on Tuesday. (Yonhap)

The main labor union of Seoul Metro, which operates subway Line Nos. 1 through 8 said Tuesday that it will launch a full-scale strike on Dec. 6 if a deal with the company cannot be reached.

The move comes after more than 70 percent of the Seoul Transit Corp. Labor Union members, the union representing about 60 percent of the Seoul Metro workforce, voted this month in favor of a strike to demand better working conditions, including a wage increase of more than 2.5 percent.

The unionized workers, however, said they would continue to negotiate with the company until the day before their planned strike to prevent it from happening.

"The union will remain committed to resolving the issue through negotiations until the very end so that (the two sides) can reach a settlement. The purpose of the strike is not to stop the subway but to stop unfair policies," said Kim Tae-kyun, chairman of the Seoul Transit Corporation's Labor Union.

Concerns over major disruptions to railway services are escalating as the Korean Railway Workers' Union, responsible for subway operations in the capital and national train services, threatens an indefinite general strike early next month.