Unionized workers at Hyundai Motor Co. were again set to stage a partial walkout Friday, further undermining the carmaker's output and sales.

According to union leaders at Hyundai, some 15,000 workers will put down their tools for four hours from 11:30 a.m., while another 13,000 union members who belong to the company's second work shift will follow suit for four hours from 8:20 p.m.

The partial strike will mark the third of its kind just this week, and the eighth since the union and management launched wage negotiations earlier in the year.

The company says labor strikes have so far caused a cut of some 26,000 cars, worth about 600 billion won ($544 million), in total output.

The company and the labor union have held 16 rounds of negotiations, but apparently have failed to narrow their differences.

The union is demanding an average 7.2-percent wage hike, along with 30 percent of the company's net profit from the previous year as a performance bonus.

The management reportedly has not yet tabled a countermeasure.

Union leaders earlier demanded that the company respond when they meet again on Wednesday for the 17th round of negotiations. (Yonhap)