Japan's exports fell in May for the first time in eight months as big automakers like Toyota were hit by sweeping U.S. tariffs, and the failure of the Asian nation to clinch a trade deal this week will likely pile pressure on its fragile economy.

TOKYO—Japan’s exports fell for the first time in eight months in May, bolstering views that the impact of President Trump’s tariffs could tie the Bank of Japan’s hands on rate hikes. Exports, a main engine of growth for Japan’s economy,