Buses wait for passengers at a bus stop near Seoul Station in central Seoul, Feb. 26. (Yonhap)

Unionized Seoul bus drivers could go on a general strike on Thursday, raising concerns over a major public transit disruption in the city.

The Seoul Bus Labor Union, which has nearly 18,000 members at 65 companies, under the Korean Automobile and Transport Workers' Federation, said on Tuesday that it will begin the strike at 4 a.m. Thursday, pending a majority vote of the members on Tuesday. The union will sit with the city government for final negotiations on Wednesday afternoon and go on strike if they fail to reach an agreement by midnight on the same day.

The union has demanded wage hikes, a revision of the salary system and the abolition of compensation discrimination for contract workers since late December. The Seoul Metropolitan Government has accepted none of the demands, it said.

For instance, over the past five years, the average wage of bus drivers in Incheon has risen 5.54 percent annually, but the average wage of bus drivers in Seoul has risen only 2.98 percent annually, according to the union.

The union stressed that despite seven rounds of negotiations over the past three months, the union and the city government have failed to narrow their differences.

If they decide to walk out, some 98 percent of buses that run in Seoul will be affected, according to the union. Also, it will be the first time in 12 years for city buses to stop operating in Seoul.

The Seoul Metropolitan Government said on Tuesday that it will carefully monitor how negotiations proceed, adding that it will prepare emergency measures in case the union goes on strike. Such emergency measures include increasing the number of subway trains during commute times and extending the last train by an hour.