A UN-owned ship arrived off war-torn Yemen on Sunday for a risky operation to pump more than a million barrels of oil from a decaying tanker and prevent a catastrophic spill. After years of tense diplomacy between the United Nations, Yemen’s Huthi rebels and the internationally recognised government, the Nautica will soon moor alongside the FSO Safer, a rusting super-tanker in the Red Sea. The delicate operation to transfer 1.14 million barrels of Marib Light crude to the Nautica, bought by the United Nations for the operation, is expected to begin in the coming days. Despite stringent safety checks, concerns remain about a spill or an explosion. The Safer is carrying four times as much oil as was spilled in the 1989 Exxon Valdez disaster off Alaska. “The risk is high. The risk is very high,” said Mohammed Mudawi, the UN Development Programme (UNDP) project manager for the ship Safer. “But we are hoping with the completion of the project that this will be eliminated.” Maintenance operations on the Safer were suspended in 2015 because of Yemen’s war, and the UNDP has for years warned it could “explode at any time”. A major spill could result in ecological disaster, devastate Yemeni fishing communities, and close lifeline ports and desalination plants. The potential spill — which could cost more than $20 billion to clean up — would possibly reach Saudi Arabia, Eritrea, Djibouti and Somalia, the UN has warned. The Iran-backed Huthis seized the capital Sanaa in 2014 and have been fighting a Saudi-led coalition since March 2015, in a conflict that has cost hundreds of thousands of lives and left most Yemenis dependent on aid. Scorching summer temperatures, ageing pipes and sea mines lurking in surrounding waters all pose threats to the operation, which has been under preparation since late May by experts from the private company SMIT Salvage. The team has inspected the vessel, arranged transfer pumps and hoses and pumped inert gas into cargo tanks to lower the risk of an explosion, David Gressly, the UN’s resident coordinator for Yemen, told the Security Council on Monday. Working at the height of summer, when on-deck temperatures soar above 50 degrees Celsius (122 degrees Fahrenheit), is an additional hazard, said Nick Quinn, a senior adviser for the project. “It becomes really hot, really quickly,” Quinn said, noting that this increases the odds of “slips, trips and falls” on deck for workers donning heavy personal protective equipment. The 47-year-old Safer has been moored off Yemen’s coast since the 1980s, when it was converted into a floating storage and offloading unit. The Nautica sailed from Djibouti on Saturday. Out past mangrove stands and other tankers bearing gas and grains, the Safer’s position — around 50 kilometres (30 miles) from the port of Hodeida — is rich in the type of wildlife that would be devastated by a spill. When AFP visited the Safer on Saturday, dolphins flashed their fins within sight of the ship, and cormorants could be seen on the rudder, which they have made their home for years. Mudawi said lingering concerns about the Safer’s infrastructure require oil-pumping to start during the day, at least 10 hours before sunset, to ensure all connections are secure and can monitor for leaks. Once underway, UN officials expect the transfer of oil from the Safer to the Nautica to take about three weeks. The saga won’t end there, however, because the question of who owns the oil will still need to be resolved by the warring Yemeni factions. The Nautica, once it has taken the Safer’s oil, will be renamed Yemen, and will stay in the area as ownership talks continue. “Once we transfer the oil, we would have to then take care of the new vessel,” said Edrees al-Shami, the Huthi-appointed executive general manager of SEPOC, the Yemeni oil and gas company. Shami’s appointment is not acknowledged by the internationally recognised government, which has named its own SEPOC head. “So we move the problem from an older, ageing vessel to a newer vessel,” Shami said. “But the sea conditions are very rough, and if you don’t maintain it for a while then you go back to the same problem.”