The UN said the emergency part of a two-stage operation would see the toxic cargo pumped from the storage platform to a temporary replacement vessel at a cost of $79.6 million.
The United Nations has said it is seeking nearly $80 million for an emergency operation to prevent a catastrophic oil spill in the Red Sea off war-ravaged Yemen.
The 45-year-old tanker FSO Safer, long used as a floating oil storage platform with 1.1 million barrels of crude on board, has been moored off the rebel-held Yemeni port of Hodeidah since 2015, without being serviced.
"The Safer is at imminent risk of a major spill, which would create a humanitarian and ecological catastrophe centred on a country already decimated by more than seven years of war," the United Nations said in a statement.
"International support — including funding — is needed now to implement the UN-coordinated plan to address the threat before it is too late."
The UN said that the emergency part of a two-stage operation would see the toxic cargo pumped from the storage platform to a temporary replacement vessel at a cost of $79.6 million.
In a second phase, a replacement platform would be installed.
Massive ecosystem devastation
At a press conference in New York, the UN humanitarian coordinator for Yemen, David Gressly, said recourse to another ship would cost around $25 million.
"We need to finish this operation by the end of September to avoid the turbulent winds and currents that start in October, November, December, increasing the risk in conducting any operation," Gressly said.
The UN stressed that "the plan cannot begin without donor funding," adding that the Netherlands will host a donor meeting.
It said "rapid donor commitments of funds" were needed to begin work by the second half of May.
Yemen's Houthi rebels already agreed on a "framework for cooperation" with the United Nations on the issue last month.
The UN has said an oil spill could destroy ecosystems, shut down the fishing industry and close the lifeline port of Hodeidah for six months.