DUBAI, United Arab Emirates — An Arab military coalition invaded Yemen’s main Red Sea port Wednesday, threatening to worsen what is already the world’s most severe humanitarian disaster by disrupting the pipeline that millions of Yemenis rely on for food and other supplies.
The air and ground attack by forces loyal to Saudi Arabia and the United Arab Emirates was aimed at tipping the balance in Yemen’s long-running civil war and driving Iranian-backed rebels out of the port of Hodeida. But sustained fighting there could produce one of the bloodiest urban battles of the war, deepening what is already a catastrophic humanitarian situation.
After years of war, 8 million of Yemen’s estimated 28 million people are at risk of starvation, according to the United Nations and aid agencies. About a quarter of a million people in Hodeida, a city of 600,000, are in danger of injury or death in an urban assault, they said.
But a battle there would have consequences far beyond the city, whose port is the main entry point for aid to the rest of the country.
“This attack risks more people dying, but it also risks cutting the lifeline of millions of Yemenis,” said Jolien Veldwijk, the acting country director in Yemen for the aid agency Care International. “Food imports already reached the lowest levels since the conflict started and the price of basic commodities has risen by a third. We are gravely concerned that parts of the population could experience famine.”
The Saudis and Emiratis intervened in the war three years ago with hopes of a quick victory over the Houthi rebels, an armed movement with ties to Iran. Instead, the two nations have been stuck in a quagmire.
With the assault on Hodeida, they were hoping for a symbolic victory over the group that would give the neighboring countries an upper hand in peace negotiations.
The Houthis still control the capital, Sanaa, as well as territories in northern Yemen, their ancestral lands.
“The liberation of the city and port will create a new reality and bring the Houthis to the negotiations,” Anwar Gargash, the Emirates’ state minister for foreign affairs, said on Twitter on Wednesday.
The United States has backed the Saudi-led coalition in this war but US military officials, including Defense Secretary Jim Mattis, have warned their Arab allies that the assault could end in failure both militarily and politically, and result in further civilian suffering.
An increasing number of Republican and Democratic lawmakers in Congress are criticizing the US role, accusing the Pentagon of being complicit in the bombing campaign.
Nine Senate Republicans and Democrats wrote to Mattis and Secretary of State Mike Pompeo on Tuesday, expressing “grave alarm” that the offensive would worsen the humanitarian crisis in the country.
“The US must now withdraw all its military support of the Saudi and UAE military coalition,” Representative Ted Lieu, Democrat if California, a former Air Force lawyer, said in a separate e-mail Wednesday. “The US already has blood on its hands in the Yemen crisis, we should not make them even bloodier.”
Yemeni troops, trained and financed by the United Arab Emirates, led the ground offensive Wednesday, which began around daybreak on the southern edge of the city. There were also airstrikes on two pro-Houthi neighborhoods in the same area, according to residents.
The Emiratis have signaled that they are planning to launch a separate naval offensive to take the port.
Aid workers who have remained in Hodeida said the center of the city remained mostly quiet.
Two diplomats familiar with the situation said that the Saudi-Emirati coalition aimed to seize the port facilities, but by late afternoon that planned assault did not appear to have started.
The United Nations, which had been frantically trying to unload two shiploads of food aid before the hostilities broke out, was setting up distribution hubs of emergency relief and food packets in the event of large civilian evacuations from the city.
The Hodeida operation began while Washington’s attention was still focused on the summit meeting between President Trump and North Korean leader Kim Jong Un. It was not immediately clear what role, if any, US military advisers would play in the campaign. The New York Times reported last month that US Army commandos were helping to locate and destroy caches of ballistic missiles and launch sites that Houthi rebels were using to attack Saudi cities.
Since 2015, the United States has provided the Saudi-led air campaign in Yemen with air-to-air refueling, intelligence assessments, and other military advice, but even those roles have been contentious.
The Pentagon insists that all of its military aid is noncombat assistance, like advising the Saudi Air Force on adopting bombing practices that kill fewer civilians. But at the same time, defense contractor Raytheon is courting lawmakers and the State Department to allow it to sell 60,000 precision-guided munitions to the Saudis and Emiratis in deals worth billions of dollars.
Major Adrian J. Rankine-Galloway, a Pentagon spokesman, said Wednesday that intelligence-sharing procedures had not changed in the prelude to the offensive, and that the United States was not providing specific information on Houthi targets for Saudi Arabia or the United Arab Emirates.
Earlier in the week, US officials repeated their warning about an assault on Hodeida to the Emiratis.
Pompeo said he had spoken to Emirati leaders “and made clear our desire to address their security concerns while preserving the free flow of humanitarian aid and lifesaving commercial imports.”
He said the United States expected “all parties” to work with the UN special envoy for Yemen and to “support a political process to resolve this conflict.”