Labor Minister Kim Moon-soo speaks during a meeting at his office in Seoul, Thursday. Courtesy of Ministry of Employment and Labor

The government warned of stern action on Thursday as tens of thousands of rail workers plan to go on a strike that would paralyze train operations across Korea next week.

Speaking to high-ranking officials at a meeting in Seoul, Labor Minister Kim Moon-soo urged unionized workers to retract their walkout plan, set to begin on Dec. 5, saying that he would strongly respond to any unlawful actions.

"Their fight, which would hold the economy and citizens' daily lives hostage, will not be able to garner support from the public ... Their actions cannot be justified," he said. "We will take stern measures against any unlawful actions with a zero-tolerance approach."

Lee then called on the workers to return to the negotiating table.

"In cooperation with the transport ministry, the city government in Seoul and the education ministry, we will try our best to resolve the pending issues through talks," he said. "If they proceed to hold a strike, we will ensure to minimize the inconvenience to citizens with prompt action in response."

A subway platform is crowded with people inside Gangnam Station in southern Seoul, Thursday. Newsis

This statement comes as employees at the Seoul subway and KTX operators threaten to halt all operations nationwide indefinitely if their demands are not met.

One of their key demands is to hire more workers to handle safety-related work. They say a staff shortage has pushed many to work overtime and to do jobs they are unfamiliar with. They also demand that train operators directly hire workers to do such work instead of outsourcing it to subcontractors.

The Korean Confederation of Trade Unions, a militant umbrella union that represents them, vowed to fight on in a statement released later that day.

"Our strike is a justifiable one. It is a fight for the safety of the people. The rail operators say they will reduce the number of safety workers despite repeated accidents," the organization said. "The labor minister, who is supposed to protect the rights of workers, is now trying to stifle them. He should step down."

So far, there are no signs of compromise. If the talks collapse, the planned strike is expected to cause massive service disruptions. Since Nov. 18, train services have already been slower than usual, with workers holding a "work-to-rule" protest, causing delays on several subway lines and some other train services in the capital region.

Work-to-rule refers to the practice of strictly following job descriptions, where workers perform only the minimum required tasks. It is a form of industrial action that can affect efficiency and productivity.