GENEVA (Reuters) - As forces of the Saudi-led military coalition close in on the main Yemeni port city of Hodeidah, aid agencies fear a major battle that will also shut down a vital lifeline for millions of hungry civilians.

Senior aid officials urged Western powers providing arms and intelligence to the coalition to push the mostly Sunni Muslim Gulf Arab allies to reconvene U.N. talks with the Iran-allied Houthi movement to avoid a bloodbath and end the three-year war.

A coalition spokesman said on Tuesday that forces backed by the coalition were 20 kms (12 miles) from the Houthi-held city of Hodeidah, but did not specify whether there were plans for an assault to seize the Red Sea port, long a key target.

“The coalition ground forces are now at the doorstep of this heavily-fortified, heavily-mined port city,” Jan Egeland, secretary-general of the Norwegian Refugee Council, told Reuters. “Thousands of civilians are fleeing from the outskirts of Hodeidah which is now a battle zone.”

“We cannot have war in Hodeidah, it would be like war in Rotterdam or Antwerp, these are comparable cities in Europe.”

Troops from the United Arab Emirates and Yemeni government are believed to lead coalition forces massing south of the city of 400,000, another aid official said, declining to be named.

Last week U.N. aid chief Mark Lowcock urged the Saudi-led coalition that controls Yemen’s ports to expedite food and fuel imports. He warned that a further 10 million Yemenis could face starvation by year-end in addition to 8.4 million already severely short of food in the world’s worst humanitarian crisis.

“LOOMING BATTLE”

“Hodeidah, the so-called big battle, has been looming now for 18 months with ups and downs,” Robert Mardini, Middle East regional director for the International Committee of the Red Cross (ICRC), told Reuters.

“It’s a densely-populated area where any military scenario will risk coming at a huge human cost.”

The coalition is carrying out air strikes in Yemen in support of restoring the internationally-recognized government, while Houthis have launched missiles into Saudi Arabia. Some 10,000 people have been killed and 3 million displaced.

Yemen traditionally imports 90 percent of its food, mainly through Hodeidah where U.N. inspectors check ships to ensure they do not carry weapons.

“It remains a lifeline for the highlands where close to 70 percent of Yemenis live. It’s about the need to have commercial imports,” Mardini said.

“Despite all the measures put in place by the Coalition to improve imports, what is reaching Hodeidah is very short of the needs.”

Egeland called for Western powers - led by Britain, the United States and France - and Iran, which is allied to the Shi’ite Houthis, to help avert disaster. “The situation is screaming for more robust diplomacy on both sides”.

“We are now in a race against the clock, to really get enough supplies in through Hodeidah which is very difficult given the continued severe restrictions on fuel and other imports by the coalition.

“War would mean nothing coming through.”