A Boskalis support vessel is due to leave Rotterdam on Friday to remove more than 1m barrels of oil from a decaying tanker off the coast of Yemen.

The Dutch company confirmed on Thursday that it had reached a final agreement with the United Nations Development Programme (UNDP) to oversee the transfer of oil from the 406,600-dwt floating storage and offloading unit Safer (built 1976).

The 99-loa Boskalis multipurpose support vessel Ndeavor (built 2013) will sail to Djibouti over the next three weeks with the equipment needed for two months of on-site preparations, the ship-to-ship transfer and clean-up.

The oil will be transferred from the Safer to the 307,300-dwt VLCC Nautica (built 2008), bought from Euronav. The Nautica is expected to arrive at the site off Yemen’s Red Sea coast in May.

The Safer will be towed to a green scrapping yard after it is cleaned.

Experts have warned for months of the risk that the decaying single-hulled Safer could explode or break up, leading to a spill four times the size of the Exxon Valdez disaster.

The UN has raised about $100m but needs a further $29m to complete the operation. The UK and Dutch governments will host a fundraising event next month.

Boskalis chief executive Peter Berdowski said: “We are extremely delighted that these efforts and the perseverance of the UN to raise the necessary funds has brought us to this agreement.

“Following a long planning period, our salvage experts are keen to get to work and to remove the oil from the Safer.”

UNDP administrator Achim Steiner said the agreement with Boskalis subsidiary Smit Salvage to deploy a team to the region “marks another critical milestone of the ‘Stop Red Sea Spill’ operation”.

“We look forward to working with Boskalis and other leading experts to prevent a humanitarian, environmental and economic disaster.”