STORY: After U.S. and British forces launched dozens of air and missile strikes against the Houthi militant group in Yemen, President Joe Biden on Friday said Washington and its allies would continue to respond to attacks on shipping and navigation in the Red Sea.

“We will make sure that we respond to the Houthis if they continue this outrageous behavior along with our allies.”

Biden made the remarks at a campaign stop in Pennsylvania.

Thursday saw U.S. and allied strikes hit military bases near airports in Yemen’s capital Sanaa, a naval base at Yemen’s main Red Sea port Hodeidah, and military sites near the coast.

The Houthis, an Iranian-backed faction who have controlled most of Yemen for nearly a decade, said five fighters had been killed in a total of 73 air strikes.

They vowed to retaliate and continue their attacks on shipping, which they say are intended to support Palestinians against Israel.

On Friday, Houthi supporters rallied en masse, burning American and Israeli flags in the streets.

A United Nations spokesperson warned all parties to weigh the risks of a wider regional war.

“We are just extremely worried about the risks and the greater risks of escalation of this.”

“So escalation is already happening. The question is how far it goes.”

Malcolm Chalmers is the deputy director of the Royal United Services Institute, a defense think tank.

He said for the Houthis, they have to weigh the costs and benefits of continued attacks on global shipping.

“Houthis, on the one hand, they are getting a lot of street credibility, a lot of support within Yemen as well as in the wider Arab world, for, as they see it ,standing up against Israel and its supporters in the West. On the other hand, the primary Houthi interest is maintaining and consolidating its position within Yemen.”

QUESTION: “Are you willing to call the Houthis a terrorist group, sir?”

BIDEN: “I think they are.”

Biden on Friday said he thought the Houthis were a terrorist group. The U.S. and UK were among ten signatories to a joint statement defending the airstrikes and warning of further action to protect the free flow of Red Sea trade if the Houthis did not back down.

Notably, Italy, Spain and France did not come out in support of the operation.