The United Nations mobilized Monday to avert a "fierce, bloody battle" for a key port in Yemen that provides a lifeline for food, medicine and other vital supplies.

UN Secretary-General Antonio Guterres met with Yemen's foreign minister at UN headquarters in New York amid warnings that an attack on rebel-held Hodeida was imminent.

Guterres said his envoy Martin Griffiths was locked in "intense negotiations" with Yemen's rebel Huthis, Saudi Arabia and the United Arab Emirates to find a "way to avoid the military confrontation in Hodeida."

During his meeting with Yemen's new Foreign Minister Khaled Alyemany, Guterres stressed that "everyone should redouble efforts to find a political solution and avoid a fierce, bloody battle for Hodeida," UN spokesman Stephane Dujarric said.

The United Nations pulled all of its international staff out of Hodeida early Monday morning.

For the past two weeks, Yemen government troops backed by the coalition have been closing in on Hodeida, which they claim is being used by Huthi rebels to smuggle weapons.

The Security Council met behind closed doors at Britain's request after London told aid agencies on the ground that it had received a warning from the United Arab Emirates of an imminent attack.

The United Nations has warned that up to 250,000 people were at risk if the coalition moves ahead with an all-out offensive to take the Red Sea port.

UN aid chief Mark Lowcock said an attack on Hodeida would be "catastrophic" and that aid agencies were hoping to "stay and deliver" in Yemen, which the UN describes as the world's worst humanitarian crisis.

Yemen relies on imports for 90 percent of its food, and 70 percent of the imports transit through Hodeida, Lowcock told reporters after briefing the council.

Griffiths, who briefed the council by video conference from Amman, has revived a year-old plan to turn over Hodeida port to a neutral party, diplomats said.

Hoping for a resolution 

Following the closed-door council meeting, Russian Ambassador Vassily Nebenzia, who is council president this month, called for de-escalation and said the top UN body would be "closely" following developments.

"We are hoping for the efforts of the special envoy to bring a positive resolution. We left it in his hands for the time being," Nebenzia told reporters.

The council did not specifically call on the coalition to refrain from attacking Hodeida and diplomats said there had been much discussion over the president's statement to the press.

US Secretary of State Mike Pompeo said he had spoken with Emirati leaders and urged them to work with the United Nations but his statement fell short of warning the coalition against launching an all-out offensive.

"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.

Griffiths is set to present on June 18 a new peace plan for Yemen, but he has warned that military action could derail that effort.

Eleven humanitarian aid agencies, including Oxfam and Save the Children, separately urged British Foreign Secretary Boris Johnson to threaten to cut off British support to the coalition if it attacks Hodeida.

"If an attack does take place, casualties on all sides will be high, with a likely catastrophic impact on the civilian population," they wrote in a letter to the foreign secretary.

More than 22 million people in Yemen are in need of aid -- 8.4 million of whom are on the brink of starvation, according to the United Nations.

Since 2015, Saudi Arabia has been leading a military campaign to push back the Huthis and restore the internationally recognized government to power.

The conflict has left nearly 10,000 people dead in Yemen, already the Arab world's poorest country.