The United States said Wednesday that it will put Yemen’s Houthis back on a list of “terrorist” entities, but the announcement failed to deter the Iran-backed rebels, who responded by attacking a US-owned ship.

The Houthis have already faced multiple rounds of air strikes in response to their targeting of merchant vessels in the Red Sea, and vowed after the designation announcement that they would continue attacks they say are in support of Palestinians in Gaza, where Israel is battling the militant group Hamas.

“The Department of State today is announcing the designation of Ansarallah, commonly referred to as the Huthis, as a Specially Designated Global Terrorist group, effective 30 days from today,” Secretary of State Antony Blinken said in a statement.

“The Houthis must be held accountable for their actions, but it should not be at the expense of Yemeni civilians,” he said.

“During the 30-day implementation delay, the US government will conduct robust outreach to stakeholders, aid providers, and partners who are crucial to facilitating humanitarian assistance and the commercial import of critical commodities in Yemen,” Blinken said.

US National Security Advisor Jake Sullivan said the designation “is an important tool to impede terrorist funding to the Huthis, further restrict their access to financial markets, and hold them accountable for their actions.”

“If the Huthis cease their attacks in the Red Sea and Gulf of Aden, the United States will immediately reevaluate this designation,” Sullivan said in a statement.

The Houthis, however, said they would not call off their strikes.

“We will not give up targeting Israeli ships or ships heading towards ports in occupied Palestine… in support of the Palestinian people,” the group’s spokesman Mohammed Abdelsalam told Al Jazeera TV, adding that they would respond to new strikes on Yemen by the United States or Britain.

While the Houthis say they have been attacking Israeli-linked vessels, Washington says dozens of countries have connections to the ships that have been targeted.

The rebels have also declared American and British interests “legitimate targets,” and Huthi military spokesman Yahya Saree said in televised remarks that they targeted a US vessel called the Genco Picardy in the Gulf of Aden.

The US Central Command (CENTCOM) confirmed the vessel had been targeted on Wednesday, saying a drone was launched from Huthi-controlled territory in Yemen and hit the US-owned and -operated, Marshall Islands-flagged bulk carrier ship.

“There were no injuries and some damage reported. M/V Genco Picardy is seaworthy and continuing underway,” CENTCOM said in a social media post.

The “terrorist” designation is part of Washington’s strategy to put pressure on the Huthis, which also includes military action against them, and the establishment of an international coalition to help protect shipping from the rebels’ attacks.

On Tuesday, the US military said it destroyed four anti-ship missiles in Yemen that posed an imminent threat to military and civilian vessels.

The United States and Britain targeted nearly 30 sites in Yemen with more than 150 munitions last week, while American forces later attacked a Huthi radar site in what was described as “a follow-on action” related to the previous strikes.

In 2021, US President Joe Biden’s administration removed his predecessor Donald Trump’s last-minute designation of the Huthis as both a foreign terrorist organization and a specially designated global terrorist group.

The removals came in response to fears from aid groups that they would need to pull out of Yemen as they are obliged to deal with the rebels, who effectively are the government in vast areas including the capital Sanaa.

The United States decided to use the specially designated global terrorist designation now because it “provides better flexibility to achieve the aims that we have in terms of carving out and safeguarding humanitarian assistance, as well as the broader well-being of the people of Yemen,” a senior administration official said.