The U.S. and its allies issued a firm warning to Houthis in Yemen on January 3, telling the group to stop attacks on shipping in the Red Sea or face “consequences.”

“The Houthis will bear the responsibility of the consequences should they continue to threaten lives, the global economy, and free flow of commerce in the region’s critical waterways,” read a joint statement from the US and 12 other countries.

The US wanted to “very clearly send a warning to the Houthis,” a senior administration official told reporters on January 3.

The Houthis have attacked commercial ships with drones, small boat raids, and missiles, including the “first time anti-ship ballistic missiles have been used anywhere, let alone against commercial ships,” according to the senior administration official.

The US has defended against Houthi attacks with fighter jets and Navy missile defense systems. British and French ships have also shot down drones launched by the Houthis.

The US military has prepared strike options against Houthis should the Biden administration decide to use force against targets in Yemen, according to US officials.

British Defense Secretary Grant Shapps has said the UK is “willing to take direct action” if attacks continue.

“I would not anticipate another warning” before the US might take more forceful action, the US senior administration official added.