Shares in Hyundai and Kia, South Korea's leading automakers, sold off after the country struck a trade pact with the U.S. The country now faces a 15% [tariff on auto exports](

Hyundai Motor Co. and affiliate Kia Corp. could face as much as $5 billion in additional costs this year under a new trade agreement between the US and South Korea that imposes a 15% import tariff on automobiles.

Hyundai Motor and Kia are accelerating efforts to localize their parts supply chains in the United States in a bid to offset mounting tariff burdens—a move that could severely impact South Korea’s auto parts industry.