Lord David Cameron has warned that Britain could launch further strikes on the Houthi rebels in Yemen if the group continues to attack cargo ships in the Red Sea.
The foreign secretary said that he is "prepared to back words with actions" if the group keeps targeting the flow of goods in the vital trade route.
It comes after British forces bombed Iranian-backed Houthi militant sites in Yemen in a joint operation with the US this week.
More than 100 precision-guided bombs and missiles were used to attack 60 targets ranging from radar systems, drone storage and launch sites to missile storage and launch facilities and command and control nodes.
Lord Cameron spoke out after the Iran-backed rebels warned that British and American strikes will not go without "punishment or retaliation".
He wrote in the Sunday Telegraph: “They’ve attacked ships from countries all over the world, heading to destinations right across the globe.
“[They are seeking to] deny passage to ships, vital supply chains are threatened and prices will go up in Britain and across the globe.
“Attacks against merchant and commercial shipping are completely unacceptable. They had to stop. And if they did not, we would have to take action.
“The Houthis chose to escalate. The number of attacks accelerated – and the severity of those attacks increased.”
His stance echoes that of Joe Biden who said on Saturday: “We will make sure that we respond to the Houthis if they continue this outrageous behaviour, along with our allies.”
Support for the Houthi was heard among some of the pro-Palestinian marchers who took to the streets of London on Saturday.
Shouts were recorded of some marchers shouting: “Yemen, Yemen make us proud, turn another ship around.”
Lord Cameron’s note added: “Our joint action will have gone some way to degrade Houthi capabilities built up with Iranian backing. We targeted sites from which we know their attacks were launched. We will carefully assess the impact of what has been done.
“But, more importantly, we have sent an unambiguous message: what the Houthis are doing is wrong, and we are determined to put a stop to it. We will work with allies. We will always defend the freedom of navigation. And, crucially, we will be prepared to back words with actions.”
