Workers at South Korea's two top carmakers went on a partial strike Friday for the first time this year, with industry watchers saying it may cause up to 65 billion won (US$63.8 million) in combined losses.

Unionists at Hyundai Motor Co. and its sister company Kia Motors Corp. were to participate in the walkout across the country, a day after their leaders failed to work out differences with management on whether to include regular bonuses as part of ordinary wages.

The workers also plan to boycott overtime work this weekend.

Considering that similar partial strikes last year cost Hyundai some 43.5 billion won, losses from Friday and this weekend may cost the automaker similar losses, according to the sources, while 22 billion won in losses are expected for Kia.

Negotiations between the union and management stalled on whether to count regular bonuses as part of ordinary wages. Some 70 percent of 47,262 union members at Hyundai voted in favor of a partial strike on Aug. 14. Kia's union decided on a one-day walkout on Tuesday.

The ordinary wage conflict has been a key issue in many labor disputes throughout the nation this year, as the Supreme Court ruled in December that bonuses paid on a regular basis should be counted as ordinary wages.
Many firms have been uneasy over the ruling, since a hike in ordinary wages automatically leads to a rise in other payments, including overtime, holiday shifts, paid annual leave and pensions, which are all calculated in proportion to the standard wage.

Hyundai workers, in addition, are demanding an 8.16 percent, or 159,614 won, raise in basic pay and an extension of the retirement age by two years to 60 without any strings attached.

Union leaders said they will hold more talks with the top management next week but added they will go on more walkouts should negotiations fall through again.

"We, too, wish to proceed with and wrap up negotiations as quickly as possible, as we certainly do not want this strike to become prolonged," a Hyundai official said.

Ssangyong Motor Co., the local unit of Indian sports utility vehicle maker Mahindra & Mahindra, and GM Korea Co., the unit of U.S. automaker General Motors Co., successfully struck wage deals in July, accepting the union workers' demands to count regular bonuses as part of ordinary wages. (Yonhap)