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Samsung Electronics workers launched an 18-day strike Thursday after management rejected a government-mediated wage proposal that the company's largest union had accepted, sending Samsung stock down as much as 4.4%.

The walkout drew 48,000 participants — representing 38% of the company's South Korean employees — after a mediation session personally led by Labor Minister Kim Young-hoon failed to bridge the two sides' remaining differences. Speaking to reporters, Choi Seung-ho said the union had signed off on a proposal put forward by the National Labor Relations Commission chief, only for Samsung management to hold out on the one issue still dividing the parties. "We will not cease our efforts to reach a deal even during the strike," Choi said, visibly emotional as he bowed before reporters.

In a statement, Samsung pointed to the union's position on bonuses for unprofitable divisions as an example of demands the company could not accept. The company's statement warned that yielding to what it called excessive union demands would compromise core management principles, while pledging to keep communication open.

The dispute centers on Samsung's performance-based bonus structure. On the union's side, key demands include enshrining a 15% operating-profit bonus allocation in employment contracts and permanently removing the existing ceiling that caps bonus payouts at half a worker's yearly salary. Management's counter-offer included a 10% operating-profit contribution to the bonus pool and a supplementary one-time payment the company described as exceeding industry norms.