German President Frank-Walter Steinmeier said Tuesday that the U.S.’s justification for its war with Iran “does not hold water,” delivering a sharp rebuke of Washington’s rationale as questions mount about the conflict’s validity.

Speaking in Germany, Steinmeier said the United States argument that Iran posed an imminent threat because of its venture toward a nuclear weapon failed to meet the standard required under international law, calling the war avoidable and inconsistent with legal norms governing the use of force.