UN Secretary-General Antonio Guterres welcomed the news that the ship-to-ship transfer of oil from the FSO Safer, a deteriorating tanker off the coast of Yemen, to a replacement vessel has been safely concluded on Friday, his spokesman said.

The removal of oil from the Safer avoided what could have been "a monumental environmental and humanitarian catastrophe," Farhan Haq, deputy spokesman For Guterres, said in a statement.

Guterres reaffirmed the UN's commitment to successfully complete this project, including through the delivery of a specialized buoy to which the replacement vessel will be safely and securely tethered, Haq said.

"Additional funding will be needed to finish the project and remove any remaining environmental threat to the Red Sea," he said.

Haq noted that "the secretary-general urges donors to contribute funds at this crucial time to conclude this operation."

The Safer tanker was originally constructed as a supertanker in 1976 and later converted to a floating storage and offloading facility (FSO) for oil. After years of neglect because of civil conflict, the FSO Safer is on the brink of breaking up, raising concerns about a potential oil spill that could wreak havoc on the fragile marine ecosystem and exacerbate the already dire humanitarian situation in Yemen.

According to the UN Development Programme (UNDP), the cargo of oil aboard the FSO Safer has been pumped onto the replacement vessel, named MOST Yemen, in a ship-to-ship transfer that began on July 25, 2023.

As much of the 1.14 million barrels has been extracted as possible. However, less than 2 percent of the original oil cargo remains mixed in with sediment that will be removed during the final cleaning of the Safer, the UNDP said.

"There is still work to be done, but today we can say with confidence that the immediate threat of a spill has been averted," UNDP Administrator Achim Steiner said in a press release.

"Today is a great milestone," said David Gressly, the UN Resident and Humanitarian Coordinator for Yemen, who has led UN system-wide efforts on the Safer since September 2021.

"A remarkable global coalition came together under the UN umbrella to prevent the worst-case scenario of a catastrophic oil spill in the Red Sea. We need to finish the work the UN started," Gressly said.