The UN has warned that a deteriorating oil tanker off the coast of Yemen could cause environmental damage for decades. UN Environment Programme chief Inger Andersen told the Security Council on Wednesday that an oil spill from the 45-year-old <em>FSO Safer,</em> which has not been maintained for more than five years, would wreck ecosystems and livelihoods for decades. “Prevention of such a crisis from precipitating is really the only option,” she said. “Despite the difficult operational context, no effort should be spared to first conduct a technical assessment and initial light repairs.” The tanker has 1.14 million barrels of crude oil on board and is at risk of spilling it into the Red Sea, causing what UN humanitarian affairs chief, Mark Lowcock, called an "environmental catastrophe”. The tanker is moored off the coast of Houthi-held territory in western Yemen. The UN is seeking access for a mission to assess the tanker’s condition, conduct any possible urgent repairs and make recommendations for the safe extraction of the oil. The Houthis seized the capital, Sanaa, in late 2014 from the internationally recognised government of President Abdrabu Mansur Hadi. At the government's request, the Saudi-led Arab Coalition has been fighting the rebels in Yemen since 2015. The rebels agreed to give the UN access to the tanker, sources at the world body said on Sunday. Mr Lowcock expressed scepticism about the Houthi offer, recalling a similar initiative in August, which the group cancelled at late notice. “We have, of course, been here before,” he said. He urged the rebels to “take steps that will spare millions of their fellow citizens from yet another tragedy”. The <em>Safer</em> could cause an oilspill four times larger than the Exxon Valdez disaster in 1989, which involved 257,000 barrels of oil and the effects of which are still being felt more than 30 years later. A spill on that scale would cause unprecedented damage to the Red Sea marine environment, which is home to more than 1,200 species of fish, of which 10 per cent are found only there. A spill would also devastate the livelihoods of nearly four million people, with fishing stocks taking 25 years to recover. It would close the strategically important port of Hodeidah for up to six months and cost up to $20 billion (Dh74bn) to clean up. The city is Yemen’s main gateway for humanitarian aid, and weapons smuggled in by the Houthis. "The <em>FSO Safer </em>oil tanker is an environmental disaster waiting to happen and unless UN experts are allowed to access it, we are facing a catastrophic environmental threat," said Britain's Minister for the Middle East, James Cleverly. “The Houthis cannot continue to hold the environment and people’s livelihoods to ransom. "It is in everyone’s interests, especially the suffering people of Yemen, that this tanker is made safe immediately. “We will continue to use our seat on the UN Security Council to do all we can to stand up for and protect the Yemeni people." Yemen is suffering from the world’s largest humanitarian crisis, with 24 million people, or 80 per cent of the population, in need of assistance. The rapid spread of Covid-19 has added to the country’s woes, with UK-funded modelling estimating that Yemen already has more than one million infections. On Tuesday, the UAE, Yemeni government and Pakistan condemned the Houthi rebels' attempts to target civilian areas in Saudi Arabia with drones and ballistic missiles, which were intercepted by Arab Coalition forces. A day before, the Saudi-led coalition said it had intercepted and destroyed four missiles and six explosive drones launched from Yemen towards Saudi Arabia by the rebels.