The import curbs on automobiles being weighed by the U.S. administration of President Donald Trump threaten to have a far greater impact on global trade than the steel and aluminum import tariffs imposed by Washington in March over the same "national security" grounds. Shipments to the U.S. market account for 40 percent of Japan's total car exports, and possible imposition of prohibitive tariffs will likely hit hard major vehicle exporters to the U.S. such as Japan. World Trade Organization rules accept unilateral import curbs for national security reasons only as an exception, and that must not be abused as an easy measure to protect domestic industries. The Japanese government should press the U.S. not to resort to such a measure and to resolve any trade problems under the framework of multinational free trade regime.

Trump ordered Commerce Secretary Wilbur Ross last week to probe whether increased vehicle imports to the U.S. pose a national security threat to the country. The Commerce Department said it launched an investigation under Section 232 of the Trade Expansion Act to determine whether vehicle and parts imports threaten the domestic industry's health and ability to research and develop new, advanced technologies. Ross cited "evidence suggesting that, for decades, imports from abroad have eroded our domestic auto industry." Trump said "core industries" like auto and auto parts "are critical" to the strength of the United States as a nation.

The Commerce Department will report the findings of its probe to the president within 270 days. A U.S. media report said a 25 percent tariff on car imports is being considered — a sharp increase from the 2.5 percent currently charged on car imports from such countries as Japan. Such a prohibitive tariff, if imposed, would turn the imported cars less competitive and no doubt impact their sales in the U.S. market.