The United Nations is trying to avoid an environmental catastrophe off Yemen, renewing an appeal for greenlighting emergency inspection and repairs on the derelict tanker Safer, a UN spokesman said on Monday.

"We remain extremely concerned about the oil tanker off the coast of Hodeidah, which is at risk of spilling more than 1.1 million barrels of oil into the Red Sea," said Stephane Dujarric, spokesman for UN Secretary-General Antonio Guterres. "A major spill would create a major humanitarian and environmental catastrophe."

"Based on current market availability of required equipment, we would need up to seven weeks from receipt of approvals until the mission staff could arrive on-site with necessary equipment," Dujarric told correspondents at a regular briefing.

Recently, there have been published reports saying an oil leak has been spotted near the rusting vessel.

For months the world organization has been trying to send an expert mission to conduct a technical assessment and complete any feasible initial repairs that would minimize the risk of a spill.

The spokesman said UN experts have had several rounds of constructive technical discussions in recent weeks with representatives of the Houthi rebels who control the area in an attempt to agree on specifications for the proposed mission.

Based on the talks, the United Nations submitted a proposal it expects will be quickly approved, he said. International donors have committed to cover costs associated with the mission.

The tanker has been serving as an oil storage and offloading platform and has had virtually no maintenance for five years.

The United Nations has said that the tanker could spill four times as much oil as during the 1989 Exxon Valdez disaster off Alaska.

There also have been published reports the Houthis believe the decaying vessel and its spill-threat serves as a deterrent to aerial bombing in the area.