The United States called on the U.N. Security Council Wednesday to take urgent action against Yemen’s Houthi rebels for attacking ships in the key Red Sea trade route and warned their longtime financier Iran that it has a choice to make about continuing to provide support to the rebels.

U.S. deputy ambassador Christopher Lu told an emergency council meeting that the Houthis have carried out more than 20 attacks since Nov. 19 – and despite losing 10 fighters in a confrontation with U.S. forces after trying unsuccessfully to board a cargo ship on Sunday, the rebel group announced Wednesday morning they had targeted another container ship.

The Houthis, who have been engaged in a civil war with Yemen’s internationally recognized government since 2014, have said they launched the attacks on ships in the Red Sea with the aim of ending Israel’s offensive in the Gaza Strip triggered by the Palestinian militant group Hamas’ Oct. 7 surprise attack in southern Israel.

International Maritime Organization Secretary-General Arsenio Dominguez told the council that as a result of the Houthi attacks, around 18 shipping companies have rerouted their vessels around South Africa to avoid the risk of being hit.