President Donald Trump has called an attack on a ship in the Strait of Hormuz a “foolish violation” of the United States’ ceasefire agreement with Iran.

Iran launched explosive-laden suicide drones at a cargo ship transiting the Strait of Hormuz on Thursday.

A ceasefire between the U.S. and Iran went into effect earlier this month and called for an immediate end to military operations from both countries and their allies.

The free flow of commerce was one of the 14 points of understanding that the U.S. and the Iran reached.