The United Nations is again calling on Yemen’s Houthi rebels to cooperate with UN inspectors who need urgent access to a dilapidated oil tanker moored off the country’s Red Sea coast. 

The FSO Safer holds 1.1 million barrels of oil, enough to spill four times as much oil into the sea than was spilled from the Exxon Valdez tanker in 1989. Experts say that time is running out to prevent a massive spill, which would devastate biodiversity in the Red Sea, disrupt one of the world’s busiest commercial trade routes and deepen Yemen’s already dire humanitarian crisis. 

The Houthis, who are fighting a Saudi-led military coalition and Yemen's internationally recognized government, seized the FSO Safer from the state-run oil company in 2015. The Iran-aligned group hasn't performed maintenance on the vessel since and has repeatedly blocked UN efforts to send inspectors. 

Inger Andersen, executive director of the UN Environment Program, told the UN Security Council on Thursday that it is critical UN inspectors gain access to the vessel and assess the likelihood of a leak. If not, Anderson warned of the major economic, social and health impacts should the FSO Safer spill oil into the sea.