A commercial ship hit by Iran-backed Houthis on Monday has created an oil slick of almost 30 km in the Red Sea as it struggles to stay afloat despite damages.

The UK-owned Belize-flagged vessel, Rubymar, is “anchored but slowly taking on water,” according to the US military. It is carrying “over 41,000 tons of fertilizer,” which makes it a huge floating hazard, since a potential spillage could worsen the “environmental disaster” caused by the vast oil slick.

“The Houthis continue to demonstrate disregard for the regional impact of their indiscriminate attacks, threatening the fishing industry, coastal communities, and imports of food supplies,” read the statement by CENTCOM.

The Houthis, armed by Iran, have targeted dozens of ships since last November, hitting at least 20 and scaring away many more. They say their attacks are solely in support of Palestinians and in response to Israel’s onslaught on Gaza. However, in recent days, they have officially added British and American ships to their list of “legitimate” targets. The Houthi attacks began days after Iran's ruler Ali Khamenei called on Muslim nations to blockade Israel.

The two countries launched a joint operation against the Houthis on January 11, hitting dozens of targets in three rounds of airstrikes –the last of which took place this week. But neither the joint operation nor the near-daily, unilateral attacks by the US military have succeeded in stopping the Houthis.

President Biden and his team seem to be struggling to find the appropriate response, perhaps because they are reluctant to confront Iran’s Revolutionary Guards IRGC), which arms, trains and is even present on the ground, “serving side by side” Houthi forces.

“We know that the Houthis maintain a large arsenal,” Pentagon’s deputy press secretary Sabrina Singh told reporters Thursday, hours after yet another ship was hit by Houthis. “They are very capable, they have sophisticated weapons, and that’s because they continue to get them from Iran.”

Iranian officials have never denied their support for the Houthis, but they say they have no operational control over the group. Some experts suggest, however, that the Houthis rely on Iran for picking their targets. The information required for such operations, they say, is gathered by the IRGC, and by the spy ship Behshad, in particular.

Curiously, the number of Houthi attacks in the Red Sea has sharply risen in the past few days, coinciding with Behshad’s return to duty after 17 days docking at Djibouti port near a Chinese military base on shore. More Houthi attacks have been recorded in the last few days than in the previous 3 weeks combined.

The Biden administration issued a statement Wednesday, “condemning” the Houthis’ “reckless and indiscriminate” attack on commercial vessels in the Red Sea. “The Houthis are behaving like a terrorist organization,” the statement read, “and contrary to what the Houthis may attempt to claim, their attacks do nothing to help the Palestinians.”

Strong words aside, the administration’s plan for stopping the Houthis is unclear. A CNN report Friday suggested that “the group is continuing to fortify its weapons stockpile inside Yemen,” quoting a US official speaking on condition of anonymity.

US forces in the region have stopped some Iranian weapons getting to Houthi-controlled areas of Yemen, but some shipments have surely slipped through the net –and more will almost certainly do so, as long as the regime in Tehran sees no harm in trying,