US President Donald Trump has announced that Iran will be directly blamed for any future attacks by Yemen’s Iran-aligned Houthi rebels on American and foreign ships in the Red Sea.

“Each shot fired by the Houthis will now be regarded as a shot fired by Iran’s guns and command,” Trump posted on his Truth Social site Monday. “Iran will be held accountable and face terrible consequences.”

Trump’s threat is part of his government’s stepped-up campaign against the Houthis, after a weekend of airstrikes that killed at least 53 individuals, according to reports. The airstrikes are likely to continue, as Iran considers its reaction to a letter Trump sent it last week concerning its developing nuclear program.

Describing the Houthis as “sinister mobsters and thugs,” Trump warned that any new attack by the group would be countered with great force. Trump also accused Iran of directing and arming the Houthis with weapons, information, and resources.

“Iran has long been playing the innocent victim, claiming to have lost control over rogue terrorists. But they are in full control, making every move,” Trump accused.

It is not yet known what triggered Trump’s most recent comments, but at the weekend, the leader of Iran’s Revolutionary Guards sought to distance Tehran from the Houthis’ behavior. In the meantime, the Houthis asserted responsibility for the firing of drones and missiles against the USS Harry S Truman aircraft carrier in the Red Sea, although the attack did not reach the ship, which remains operational in the area.

Iran has not yet made an official reaction to Trump’s declaration. Nevertheless, the Red Sea remains tense as the US continues to carry out military strikes against the Houthi rebels.