Yemen's Houthi rebels agreed to allow a United Nations mission to repair a decaying oil tanker moored off the coast that experts say could spill more than a million barrels of oil into the Red Sea.
The Iran-backed group has been in talks with UN officials about accessing the FSO Safer tanker for months, but UN spokesman Stephane Dujarric said an official letter from the Iran-backed group on Saturday confirmed that it could finally go ahead.
"It represents an important step forward in this critical work," Mr Dujarric said on Tuesday.
"The objective of the UN-led expert mission is to assess the vessel and undertake initial light maintenance as well as to formulate recommendations on what further action is required to neutralise the risk of an oil spill."
UN experts are now arranging a team of engineers and ordering the gear needed to repair the vessel, which has been stranded off Yemen's Red Sea oil terminal of Ras Issa for more than five years, Mr Dujarric said.
They expect to board the ship in January or early February next year, the spokesman said.
"Now that the UN proposal for the expert mission has been agreed, mission planning will immediately pivot towards deployment and deployment preparations," Mr Dujarric said.
"This includes the procurement of necessary equipment, entry permits for all staff, agreement on the work order system on board and logistical planning."
The rusting tanker is loaded with about 1.1 million barrels of crude oil, meaning it could spill four times as much oil as the 1989 Exxon Valdez disaster near Alaska, according to the world body.
In May, a leak into the ship's engine room threatened to destabilise it. Divers from the Safer Corporation managed to plug that leak, but experts say that the tanker could rupture at any time.
The Houthis previously let UN teams inspect the vessel for repairs but then changed their minds. Last year, the group cancelled a UN engineering visit a day before the agreed departure date.
Yemen has been riven by conflict since the Iran-allied Houthi group ousted the government from the capital Sanaa in 2014. A Saudi Arabia-led military coalition in 2015 intervened in an attempt to restore the government.