Striking workers from Hyundai Motor, affiliate Kia Corp (000270.KS) and their suppliers will hold a rally outside Hyundai Motor's headquarters in Seoul at 2 p.m. (0500 GMT), the Korea Metal Workers Union (KMWU), the umbrella union that represents the workers, said in a leaflet announcing the strike posted on the union's website.
About 40,000 Hyundai Motor union members were expected to join the walkout on Friday, while around 1,200 to 1,300 union members were due to attend the Seoul rally, a union official said.
Members of other unions and of the umbrella union were also expected to join, bringing the total expected attendance at the rally in the capital to about 3,000, the official added.
The one-day strike illustrates growing labour unrest in South Korea following the election of pro-labour liberal President Lee Jae Myung last year.
It follows a series of partial walkouts since late July that have disrupted production of 55,200 vehicles worth over 2.3 trillion won ($1.67 billion), according to estimates from Yonhap News Agency.
The labour action adds to challenges facing the automaker, which in July said it expected to miss its global sales target this year, amid growing Chinese competition in Europe and falling sales in South Korea.
Hyundai's union wants the mandatory retirement age raised from the current 60, in line with President Lee's pledge to gradually increase the limit in one of the world's fastest-ageing countries.
The union is also seeking to raise bonuses to 800% of monthly base salary from 750%, and has demanded guarantees to protect jobs as the company adopts AI and automation.
Hyundai, which owns humanoid robot maker Boston Dynamics, has said it plans to deploy humanoid robots at its U.S. plant in Georgia from 2028, with the aim of expanding their use across its production sites.
Hyundai Motor union spokesperson Kim Jin-wook said the two sides remained apart over the retirement age and bonuses, among other issues.
He said the union is open to resuming wage talks, but would discuss strike plans if the management failed to come up with "forward-looking proposals."
Hyundai Motor said it was committed to finding solutions through dialogue.
"Strike action can impact our customers, partners and operations. We are at a critical time when both sides must work together to successfully navigate the global transition to future mobility," it said in a statement.
($1 = 1,381.2700 won)
