With fuel costs soaring, the truckers are calling on the government to make permanent a minimum-pay system that is due to expire by the end of the year, and to expand benefits for truckers in other industries, including oil tankers.
The government has said it will extend the scheme for three years but rejected other union demands.
Lead organiser the Cargo Truckers Solidarity Union (CTSU) has warned the strike could stop oil supplies at major refineries and transport at major ports and industrial plants.
Earlier this week, Land Minister Won Hee-ryong said the "Safe Freight Rate" system had not been proven to improve the safety of truckers but to only raise their incomes, a reason why the government has refused to expand the scope of the scheme.
The union is asking the government to ensure big businesses are held accountable if they violate the minimum wages rule.
In June, an eight-day strike by truckers delayed cargo shipments for industries from autos to semiconductors in Asia's fourth-largest economy, costing more than $1.2 billion in lost output and unmet deliveries.
Industry giants including Hyundai Motor and steelmaker POSCO were forced to cut output by the June strike, and POSCO has warned that fresh action could slow repair works at a major plant hit by floods this summer.
The union is scheduled to hold 16 rallies across the country on Thursday morning, including at a port in Ulsan that houses Hyundai Motor's manufacturing plant.
The government is considering deploying military trucks for urgent transport, and securing more storage space in case cargoes pile up. The Korea Oil Station Association is asking gas station owners to secure enough inventory ahead of the strike, an association official said earlier.
The union has said almost all of CTSU's 25,000 members, about 6% of the country's truck drivers, will take part in the strike, joined by an unspecified number of non-union members.
(Reporting by Ju-min Park; Editing by Catherine Evans)
By Ju-min Park
