President Trump said the U.S. will impose steep levies on imports from 14 countries starting next month, heightening pressure on trading partners.

President Donald Trump unveiled the first in a wave of promised letters that threaten to impose higher tariff rates on key trading partners, but suggested that he was still open to additional negotiations and pushed off increased duties until at least Aug.

President Trump said Japan and South Korea would face tariffs of 25 percent unless they reached an agreement with the United States. Other countries received notice of higher levies.