The US believes that Iran is involved in the planning and execution of drone and missile attacks by Yemen’s Houthi group on Israel and ships in the Red Sea, a senior aide to US President Joe Biden said on Thursday.

The comments by deputy White House national security adviser Jon Finer are among the most explicit to date by a US official alleging Iranian involvement in the Houthi attacks.

Finer spoke hours after the US imposed new sanctions aimed at throttling what US officials say is Iranian financial support for the Houthi strikes.

The Houthis “would not have the weaponry, would not have the intelligence, would not have the motivation to do this, were it not for the role of the IRGC”, Finer told an Aspen Security Forum conference in Washington, using the acronym for Iran’s Islamic Revolutionary Guard Corps.

“They’re involved in the conduct of these attacks, the planning of them, the execution of them, the authorisation of them, and ultimately, they support them,” he continued.

Iran has denied any involvement in the strikes.

The Houthis say they have been staging attacks against Israel and Israeli ships in the Red Sea in response to the offensive Israel launched against Tehran-backed militant group Hamas in Gaza.

Washington has said that US warships have downed missiles and drones fired by the Houthis but the Pentagon says it is not clear that the American vessels were actually targeted. US warships also have intercepted attacks on commercial ships that the US military says were linked to multiple nations.

Finer said that the USS. Carney, a destroyer, downed dozens of missiles and drones headed towards Israel early in the Gaza conflict, calling it a “remarkable act of defence of Israeli territory”.

Asked whether US warships in the region were defending Israel, Finer said he did not know the munitions’ ultimate destination. Biden has authorised US naval vessels to down munitions passing in their vicinities, he added.

The sanctions announced on Thursday by the US treasury were part of the US response to the attacks and “enablers of the Houthis’ military capability out of Yemen”, Finer said. The sanctions targeted 13 individuals and entities for allegedly funnelling tens of millions of dollars in foreign currency to the Houthis from the sale and shipment of Iranian commodities.

The US treasury said in a statement that the IRGC, Iran’s paramilitary and espionage force, backed the scheme involving a complex web of currency exchange houses and firms in multiple countries.