The United Nations and the International Committee for the Red Cross withdrew their staff members from the besieged Yemeni port city of Al Hudaydah, fearing that an attack by forces led by the United Arab Emirates was imminent, officials said Monday.

Frantic diplomacy to stave off an attack on the city of 600,000 people and avert a potential humanitarian disaster moved to the United Nations on Monday, where the Security Council held a closed-door briefing on the situation.

“We are, at the present moment, in intense consultation,” the United Nations Secretary General António Guterres said Monday. “There is a lull in the fighting to allow for them, and I hope that it will be possible to avoid a battle for Hudaydah.”

In Washington, bipartisan efforts were underway in the Senate to warn the Emirates and its ally in Yemen, Saudi Arabia, that a military assault on Al Hudaydah could result in the United States cutting off funding for aerial refueling, which has been crucial to the Saudi air campaign there.