The United Nations was withdrawing its staff on Monday from the besieged Yemeni port city of Al Hudaydah, after member countries were told that an attack by forces led by the United Arab Emirates was imminent, according to two diplomats briefed on the matter.
The evacuation followed a weekend of frantic diplomacy by international officials to stave off what many see as an impending humanitarian and military catastrophe in Yemen’s continuing civil war.
Al Hudaydah, the focus of the latest crisis, is a crucial port city of 600,000 people that is the gateway for approximately 80 % of the foreign humanitarian aid entering Yemen. For the last two years, it has been held by Iran-backed Houthi rebels, who ousted the government three years ago.
Fighting the Houthis is a mix of Yemeni tribal forces and Islamist groups backed by the United Arab Emirates and Saudi Arabia. That coalition has long sought to seize the city and in that way deny the Houthis a vital piece of territory, while giving the Arab nations an upper hand in peace negotiations.
The Arab-led coalition and the American military say the rebels have been smuggling arms through Al Hudaydah, including missiles that the Houthis have used to attack Saudi Arabia.
But any full-scale attack on the port would be highly contentious. American officials have warned the Emirati and Saudi governments that an offensive would result in a quagmire. The United Nations says it could cause more than a quarter of a million civilian casualties.
Yemen is already classified as the world’s worst humanitarian disaster. More than 75 percent of the population is dependent on food aid and millions are on the brink of starvation, while the war shows little signs of abating.
The United Nations Special Envoy to Yemen, Martin Griffiths, has been working to forge an agreement with the Houthis to hand over control of the city and its port to the international body, depriving the Emiratis and Saudis of their rationale for an attack. Diplomats familiar with the situation say that while he has made progress, it is unclear whether Riyadh and Abu Dhabi would back any such breakthrough.
Part of the calculations is the apparent desire of Saudi Arabia and the United Arab Emirates to strike a huge blow against the Houthis, whom they consider a proxy for their regional nemesis, Iran. Yemen’s civil war began with a breakdown of political talks in the wake of Arab Spring protests that toppled former President Ali Abdullah Saleh. Longstanding political divisions over power sharing gave way to military conflict, giving rise to a variety of short-term alliances across the impoverished and deeply divided nation.
The current configuration of forces pits the predominantly Shiite Houthi rebels, who were long marginalized by Saudi-backed proxy groups in Yemen, against Sunni tribal and other militia groups that are backed by the Emiratis and Saudis.
Diplomats involved in behind-the-scenes negotiations say that the United Arab Emirates officially warned the British government on Friday that an attack on Al Hudaydah was imminent. The Emiratis said they would give three days for humanitarian workers and nongovernmental organizations to flee the city.
The International Committee for the Red Cross removed its staff from the city over the weekend.
The United Nations worked out terms with the Houthi rebels on Sunday and planned to have its foreign staff evacuate from the city in multiple convoys on Monday. United Nations agencies planned to leave in place a skeleton crew of Yemenis from Al Hudaydah to try to keep their humanitarian mission going.
Diplomats familiar with the situation say they believe that the Emiratis, who are leading the push for an attack, are looking to launch their planned assault while Washington’s attention is focused this week on the summit meeting between President Trump and the North Korean leader Kim Jong-un.
The United States has backed the Arab states in the war, but Abu Dhabi has received powerful pushback from various American officials who see the idea of an urban assault on a densely populated city as an unmitigated disaster, in both military and humanitarian terms.
Secretary of State Mike Pompeo said in a statement that he had spoken to Emirati leaders to emphasize the American wish to keep humanitarian supply lines open and to preserve a political process between the opposing sides in Yemen.
Mr. Pompeo said that in his conversation with the Emiratis he had made clear the United States’ “desire to address their security concerns while preserving the free flow of humanitarian aid and lifesaving commercial imports,” the statement said.
The United States sells tens of millions of dollars of weapons to the United Arab Emirates and to Saudi Arabia every year, and the Trump administration has forged close ties with the crown princes of both nations. Those relationships with the White House — and the deep divisions in Washington — have emboldened the two Arab countries to push ahead with their own agendas.
Members of the Senate Foreign Relations Committee have threatened to push forward a bill to cut off some military aid to the Emirates and to Saudi Arabia, as a penalty for what they say are punitive and indiscriminate attacks in Yemen that are responsible for thousands of civilian deaths.
Defense Secretary Jim Mattis has also privately sent messages to the Arab states, cautioning against any attack on Al Hudaydah, according to two people familiar with the situation. American military officials do not want Congress to prevent military aid to the two nations, both of which are crucial allies in counterterrorism, nor do they want a vacuum of power in Yemen to result in a new incubator for extremist groups like the Islamic State and Al Qaeda.
Diplomats in the region say they believe that only more pressure from Washington will stop the planned assault.