U.S. President Donald Trump on Saturday threatened to impose a 30% tariff on imports from Mexico and the European Union starting on Aug. 1, after weeks of negotiations with the major American trading partners failed to reach a comprehensive trade deal.

In an escalation of a trade war that has angered U.S. allies and rattled investors, Trump announced the latest tariffs in separate letters to European Commission President Ursula von der Leyen and Mexican President Claudia Sheinbaum that were posted on his Truth Social media site on Saturday.

The EU and Mexico, both among the largest U.S. trading partners, responded by calling the tariffs unfair and disruptive while pledging to continue to negotiate with the U.S. for a broader trade deal before the deadline.