South Korean companies, including Samsung Electronics, are worried about Vietnam's plan to reform incentives for the high-tech sector, warning it could lead to higher costs for foreign investors and potentially undermine new investment, Korean officials have said. The warning comes amid continued uncertainty about Vietnam's trade relations with the U.S., its biggest export market. In addition to a 20% duty on imports from Vietnam applied since August, the White House has threatened 40% duties on goods relying on foreign components and possible tariffs on electronics, a sector dominated in Vietnam by Korean manufacturers.