Yemen has been engulfed in a civil war since Iranian-backed Houthis overthrew the Yemeni government and seized control of the capitol three years ago.
Saudi-backed forces have been advancing toward the port for weeks, fueling concerns the attack would spark a humanitarian crisis and major starvation. Houthi forces have fired missiles at ships previously.
"These are the last and final hours to get unconditional guarantees that the Houthis will leave the port", UAE Minister of State for Foreign Affairs Anwar Gargash told Reuters, but declined to discuss military operations.
UAE-backed Yemeni forces - drawn from southern separatists, local units from the Red Sea costal plain and a battalion led by a nephew of late former President Alo Abdullah Saleh - are fighting alongside Emirati and Sudanese troops.
More than 10,000 people have been killed since Saudi Arabia led a bombing campaign against the Houthis. "Not only does the IRC and other humanitarian aid agencies have staff on the ground working to deliver lifesaving aid, but 400,000 innocent civilian lives are at stake", Frank McManus, the Yemen country director for the International Rescue Committee, said in a statement on Wednesday.
The member countries of the Saudi-led Arab Coalition in Yemen are aiming to improve the humanitarian conditions across the areas to be liberated in Al Hodeidah city, to be on par with the other areas that have been liberated from the grip of the Houthis in Yemen's Red Sea Coast and to help the Yemeni people to overcome the dire conditions caused by the terrorist practices of the elements of the militias. The port is the main entry point for food and humanitarian aid supplies that millions rely on in Houthi-controlled areas. The support has continued despite global alarm over the coalition's air campaign against the Houthis, which has killed thousands of civilians in airstrikes that human rights groups have alleged are frequently indiscriminate.
"Parties to the conflict must now prepare to bear responsibility for any violations of International Humanitarian Law, particularly the targeting of civilians and civilian infrastructures such as medical facilities, schools and the port facilities, for which the U.N. Security Council must ensure accountability".
Yemen's United Nations humanitarian coordinator Lise Grande said a "worst case" in an assault on Hodedia would mean 250,000 people "losing everything - even their lives".
United Nations chief Antonio Guterres had said that Mr Griffiths was in "intense negotiations" in an attempt to avoid a military confrontation. However, Griffiths' recent appointment as envoy and his push for new negotiations might have encouraged the Saudi-led coalition to strengthen its hand ahead of any peace talks.
Khalid bin Salman, Saudi Arabia's ambassador to the United States, said addressing the humanitarian situation effectively "requires liberating Yemen from the control of Houthi militias" which he said disrupt the flow and distribution of humanitarian supplies.
The alliance intervened in Yemen to restore the government of President Abd-Rabbu Mansour Hadi, who was driven from the capital Sanaa and into exile in 2014.
The Houthis deny they are Iranian pawns and say their revolt is against corruption and defending Yemen from invaders. Meanwhile, the U.N. and Western nations say Iran has supplied the Houthis with weapons from assault rifles up to the ballistic missiles they have fired deep into Saudi Arabia, including at the capital, Riyadh.