The United States is standing idly by in the face of an imminent military offensive by its ally, the United Arab Emirates (UAE), on Yemen’s port city of Hudaydah, which the UN and aid groups have warned could lead to a humanitarian catastrophe there.

In the past few days, forces loyal to Yemen’s ex-president, Abd Rabbuh Mansur Hadi, backed by a Saudi-led coalition, have closed in on Hudaydah, reportedly seizing a number of nearby areas. The UAE, which is a party to the Saudi-led coalition, is playing a key role in the offensive.

The coalition, which has been waging a deadly war on Yemen since 2015, claims that the Yemeni Houthi Ansarullah movement is using the besieged port for weapons delivery, an allegation rejected by the fighters.

The Houthi movement has been both running state affairs in the absence of an effective government and defending the country against the Saudi aggression with the help of allied popular forces.

Ansarullah has pledged a firm response to a military offensive against Hudaydah. Residents of the port city are also preparing to help the Houthis against any such invasion.

Yemeni media reports over the past days suggest that people from other parts of Yemen are rushing to the port city to assist the armed forces in their counter-attacks in the wake of a potential Emirati offensive.

UAE invasion looming on horizon

On Saturday, the UAE has given the UN and foreign NGOs three days to leave Hudaydah before it mounts an attack on the Red Sea port city, which is a lifeline for aid flow into the war-torn country.

Correspondence from European donor governments to aid groups in Yemen warned that “a military assault now looks imminent.”

“The Emiratis have informed us today that they will now give a 3-day grace period for the UN (and their partners) to leave the city,” read the correspondence seen by Reuters.

UN rushing to stave off assault

Meanwhile, the UN has warned that a potential raid could cost up to 250,000 lives in Hudaydah which has a population of 600,000 people.

UN aid chief Mark Lowcock said an attack on the city would be “catastrophic” and that aid agencies were hoping to “stay and deliver” in Yemen.

However, the UN and the International Committee of the Red Cross (ICRC) have withdrawn their staff members from the key Yemeni port.

The UK government has issued guidance to aid agencies receiving British funding to leave the city. The French aid group Doctors Without Borders, known as MSF, has also suspended its operations there.

On Monday, the UN Security Council met behind closed doors over the situation in Hudaydah amid heavy fighting there.

After the meeting, Russia’s Ambassador to the UN Vasily Nebenzya called for deescalation and said the Security Council would be “closely” following the developments in Yemen.

He further expressed hope that efforts by UN Special Envoy for Yemen Martin Griffiths would bring about a positive resolution of the conflict.

Additionally on Monday, UN Secretary General Antonio Guterres met with Yemen’s self-proclaimed foreign minister, Khaled Alyemany, at the UN headquarters in New York.

During the meeting, Guterres stressed that “everyone should redouble efforts to find a political solution and avoid a fierce, bloody battle for Hudaydah,” according to his spokesman, Stephane Dujarric.

Guterres also noted that Griffiths was locked in “intense negotiations” with Yemen’s Houthi movement, Saudi Arabia and the UAE to find a “way to avoid the military confrontation in Hudaydah.”

US avoids action, gives ‘yellow light’

Meanwhile, the United States and the UK, the main sponsors of the Saudi-led war, have stopped short of taking concrete action to stop the UAE from attacking Hudaydah, merely voicing concerns over the humanitarian consequences of such an assault.

US Secretary of State Mike Pompeo said he was “closely following” the situation in Hudaydah, but refrained from demanding that the UAE hold fire.

“I have spoken with Emirati leaders and made clear our desire to address their security concerns while preserving the free flow of humanitarian aid and life-saving commercial imports,” he said in a statement on Monday.

The British government also called on the Emiratis not to press ahead with the attack. At the same time, the UK’s Department for International Development (Dfid) warned international aid groups on Saturday that diplomatic negotiations to avert the attack were failing.

Mohammed Ali al-Houthi, head of the Supreme Revolutionary Committee of Yemen, on Monday held the US responsible for any threat against Hudaydah, warning that such adventurism would result in failure.

UN officials believe that Abu Dhabi would not launch the Hudaydah attack without a green light from Washington. “So far they have a blinking yellow light from the US,” a UN official said.

The US administration is, however, under pressure from congressmen to prevent such a military action.

A bipartisan group of lawmakers at the US House of Representatives has circulated a letter calling for Defense Secretary Jim Mattis to help prevent a “catastrophic” military campaign on Hudaydah.

“We urge you to use all available means to avert a catastrophic military assault on Yemen’s major port city of Hudaydah by the Saudi-led coalition, and to present Congress with immediate clarification regarding the full scope of US military involvement in that conflict,” said a draft of the letter obtained by The Hill newspaper.

They have also called on Mattis "to dissuade the Saudi-led coalition from moving forward with this offensive and reject the provision of US logistical, military and diplomatic support for any such operation.”

Furthermore, Oxfam America aid organization has urged the US to prevent the UAE attack on Hudaydah .

“With hundreds of thousands of Yemenis at risk, this is not the time for the US, or any state, to hide behind carefully crafted disavowals. The US could threaten to end its participation in the Saudi- and Emirati-led coalition in Yemen if the offensive proceeds. It could threaten to end any broader Yemen-related defense cooperation, including arms sales to the UAE. It could threaten sanctions or other economic consequences,” it said.

Saudi Arabia and its allies launched a war on Yemen in March 2015 in support of Yemen’s former Riyadh-friendly government and against the Houthis.

The military campaign has killed and injured over 600,000 civilians, according to the Yemeni Ministry of Human Rights.

Saudi Arabia has also imposed a blockade on Yemen, which has smothered humanitarian deliveries of food and medicine to the import-dependent state.