The attacks are part of a broad response to the Gaza conflict by a so-called Axis of Resistance.
The Biden administration on Wednesday returned the Yemen-based Houthi rebels to a list of terrorist groups, U.S. officials said, in the latest attempt by Washington to stem attacks on international shipping.
Officials said the "Specially Designated Global Terrorist" (SDGT) designation, which hits the Iran-aligned group with harsh sanctions, was aimed at cutting off funding and weapons the Houthis have used to attack or hijack ships in vital Red Sea shipping lanes.
The Houthis' campaign has disrupted global commerce, stoked fears of inflation and deepened concern that fallout from the Israel-Hamas war could destabilize the Middle East.
"These attacks fit the textbook definition of terrorism," said one of three administration officials who briefed reporters ahead of the announcement on condition of anonymity.
The designation comes after American and British warplanes, ships and submarines last week launched dozens of air strikes against the Houthis, who control the most populous parts of Yemen.
The U.S. military on Tuesday carried out its latest strike against four Houthi anti-ship ballistic missiles, two U.S. officials told Reuters.
The Houthi militia movement, which says the attacks on commercial ships are aimed at supporting the Palestinians in Israel's war in Gaza, has threatened a "strong and effective response."
The attacks are part of a broad response to the Gaza conflict by a so-called Axis of Resistance - including the Houthis alongside Palestinian militants Hamas, Lebanon-based Hezbollah and Iraq's Shiite militias - with ties to U.S. adversary Iran.
"We will continue to counter and blunt Iranian malign influence wherever we can. So of course the choice to move away from Iran is now in the hands of the Houthis," said a second official, adding that the U.S. would consider lifting the designation if the attacks on shipping cease.
HUMANITARIAN SITUATION
A Saudi Arabia-led military coalition intervened in Yemen in 2015, backing government forces fighting the Houthis in a war widely seen as a proxy conflict between U.S. ally Saudi Arabia and Iran.
The Trump administration added the Houthis to two lists designating them as terrorists a day before its term ended, prompting the United Nations, aid groups and some U.S. lawmakers to express fears that sanctions would disrupt flows of food, fuel and other commodities into Yemen.
U.S. Secretary of State Antony Blinken on Feb. 12, 2021, revoked the designations in "recognition of the dire humanitarian situation in Yemen."
The United Nations describes the humanitarian crisis in Yemen as "severe" with more than 21 million people - two thirds of the population - in need of aid. It says more than 80% of the population struggles to access food, safe drinking water and adequate health services.
Blinken was on Wednesday relisting the Houthis as SDGTs, the U.S. officials said, but not as a "foreign terrorist organization," which includes stricter prohibitions on providing material support to those on the list and would mean automatic travel bans.
The former designation "provides better flexibility to achieve the aims that we have in terms of carving out and safeguarding humanitarian assistance," an official said, a reference to measures to mitigate the impact of the move on Yemen's people that Washington plans to introduce before the designation takes force in 30 days.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)