ADEN • A Saudi-led coalition geared up yesterday for an assault on Yemen's main port, preparing to launch by far the biggest battle of a three-year-old war between an alliance of Arab states and the Houthi movement that controls Yemen's capital.

The United Arab Emirates (UAE), one of the main members of the Western-backed alliance, had set the Tuesday deadline for the Iran-aligned Houthis to withdraw from the port of Hodeidah under United Nations-led negotiations or face an assault.

It would be the first time since they joined the war on behalf of Yemen's exiled government that the foreign armies have attempted to capture such a well-defended major city.

Hodeidah, Yemen's biggest port and the only one controlled by the Houthis, serves as the lifeline for the majority of Yemen's population, which lives in Houthi-ruled territory.

The UN said it was engaged in "intense" shuttle diplomacy between the Houthis and coalition leaders Saudi Arabia and the UAE to avert the attack.

It estimates that 600,000 people live in the area and, in a worst-case scenario, a battle could cost up to 250,000 lives, as well as cut off millions from aid and supplies.

Emirati-led troops have advanced along the south-western coast to the outskirts of Hodeidah under a coalition strategy to box in the Houthis in the capital Sanaa and choke off their supply lines to force them to the negotiating table.

Local military sources said hundreds of Yemeni fighters, as well as tanks and military supplies from the UAE, arrived on Monday to reinforce troops, including Emiratis and Sudanese, in al-Durayhmi, a rural area 10km south of Hodeidah.

The sources said Yemeni forces allied to the Saudi-led coalition - drawn from southern separatists, local units from the Red Sea coastal plain and a battalion led by a nephew of late former president Ali Abdullah Saleh - had advanced and were "at the doors" of Hodeidah airport.

The war pits the Houthis against the Western-backed Sunni Muslim states, which intervened in 2015 to restore the exiled government and thwart what Riyadh and Abu Dhabi see as expansionist aims of their Shi'ite Muslim foe Iran.

The Houthis, with roots in a Zaidi Shi'ite minority that ruled a thousand-year kingdom in Yemen until 1962, deny they are pawns of Iran.

The renewed push on Hodeidah comes amid increased tensions between Saudi Arabia and arch-foe Iran after the United States withdrew last month from an international nuclear agreement with Teheran, a move hailed by Riyadh and Abu Dhabi.

REUTERS