Efforts to prevent a devastating oil spill in the Red Sea are inching forward, with tens of millions of dollars raised in recent weeks to secure the rusting hulk of the FSO Safer – a tanker lying off the Yemeni coast which contains some 1.1 million barrels of oil.

The most recent donor is Saudi Arabia, which said on June 12 it would give $10 million via the King Salman Humanitarian Aid and Relief Centre (KSrelief).

This takes the total raised in recent weeks to at least $43 million. At a pledging event in The Hague on May 11, some $33 million was raised, including $8 million from The Netherlands and $2 million from Qatar. The remainder came from the European Union and eight European governments.

However, this remains far short of the $144 million which the United Nations has said is needed to make the vessel safe and to offload its cargo, which amounts to four times as much oil as was spilled during the Exxon Valdez disaster in 1989.

Of the UN’s target, $80 million is needed to fund an emergency operation to offload the oil from the Safer to another vessel. Funds are also needed to dismantle the Safer.

The Dutch government has said that, as well as the funding, the operation also depends on the willingness of the Houthi rebel group to allow access.

The ship is anchored off the south west of the Ras Isa peninsula, close to Yemen’s main Red Sea port of Hodeidah, in an area controlled by the Houthis, who have been locked in a war with Saudi Arabia and its allies since 2015.

The condition of the Safer has been a concern for years. There has been no proper inspection or maintenance work since 2015. Parts of the ship have previously flooded and it is thought to be in an increasingly delicate state. However, efforts to secure the ship and its cargo have repeatedly failed, due to a lack of safe access.

If the ship did break up – and higher winds and more volatile currents from October onwards make that more likely – then a leak of its cargo would devastate important fisheries in a wide area and marine life more generally. The livelihoods of some 126,000 Yemeni fishermen would be at risk, while some 30 million people would be affected in some way.

The cost of a clean-up following a spill has been estimated by the Dutch government at some $20 billion. The International Maritime Organization has drawn up a contingency plan should the worst happen.