Yemen’s Iran-backed Houthis announced a maritime embargo of Saudi Arabia on Monday, stepping up the US-Iran war as the rebels threatened the top oil exporter’s ability to bypass the Strait of Hormuz.

The Houthis did not say how they planned to impose the embargo, whose announcement came as Iran said it was back to a “full-scale war” with the United States, and as Washington and Tehran battled to control the strait.

Saudi Arabia and the Houthis traded fire last week for the first time in years, threatening a 2022 truce that has held despite expiring.

The exchange of fire was set off when an Iranian plane arriving from Tehran attempted to land in Sanaa, challenging Saudi Arabia’s hegemony over Yemeni skies.

The Houthis’ naval blockade, if enforced, could further strain Saudi Arabia’s economy by cutting off access to its Red Sea ports, which have been vital for oil exports as renewed fighting limits passage through the Strait of Hormuz.

The blockade is also expected to hurt global markets that rely on Saudi Arabia – the world’s leading crude exporter, producing over 10 million barrels per day – for their energy imports.

The rebels declared “a maritime embargo against the criminal Saudi enemy, based on the equation of ‘an eye for an eye’, effective immediately upon the issuance of this statement”, military spokesman Yahya Saree said.

For Farea al-Muslimi, a research fellow at the London-based Chatham House think-tank, “this is an attempt by the Houthis to basically go into a war with Saudi Arabia”.

A war “with Saudi shipment is a war with the world”, he said.

The Houthis have previously tried to cut off shipping through the Red Sea, leveraging the Bab al-Mandab Strait, a chokepoint at its southern tip which vessels must navigate when travelling to or from the Suez Canal and the Mediterranean.

They previously launched drone and missile attacks on ships transiting the strategic waterway beginning in November 2023 during the Gaza war, forcing vessels to take lengthy detours around Africa instead of travelling directly from Europe.

Yemen shares a border and coastline with Saudi Arabia, whose Red Sea port of Yanbu has been crucial for exporting oil, bypassing Iran’s effective closure of the Strait of Hormuz during its war with the US.

‘Foolish act’

The conflict erupted in late February with US-Israeli strikes on Iran, which retaliated by launching attacks across the Middle East, with the Gulf bearing the brunt of them.

The war wrought chaos in the region and sowed panic on global energy markets until Iran and the US agreed a ceasefire last month — which has since collapsed.

As tensions flared again in Hormuz, Saudi Red Sea ports have become all the more vital.

“Even if no ships are attacked, the announcement alone is likely to disrupt shipping and create uncertainty for Saudi ports,” said Mohammed al-Basha, of the US-based risk advisory Basha Report.

“Whether the Houthis move from threats to direct action remains the critical issue.”

Saree said the move was in response to Saudi Arabia’s blockade of Houthi “ports and airports” and the targeting of Sanaa airport last week, adding that they would respond to “the blockade with a blockade”.

“Any foolish act committed by the reckless Saudi enemy through all escalation will be met with a comprehensive and decisive escalation,” Saree added.

Last week, the Houthis fired missiles at an airport in the Saudi city of Abha, after Yemen’s government said it hit Sanaa airport to block a flight from Iran with a Houthi delegation on board.

The Houthis blamed the government’s backer Riyadh for the attack.

For more than a decade, aircraft entering Yemeni airspace have needed prior clearance from the Saudi-led coalition that backs Yemen’s government and says it enforces the restriction at its request.

The Houthis have been at war with Yemen’s government since 2014, in a conflict that has killed hundreds of thousands of people and triggered a major humanitarian crisis.