Efforts are under way to prevent a tanker targeted by Houthi rebels from spilling around one million barrels of oil into the Red Sea.
The Greek-owned and flagged MV Sounion was abandoned by its crew off the coast of Oman after being struck on 21 August by the Yemeni rebel group.
Private companies under the protection of European Union military forces will attempt to salvage the vessel, which has the potential to trigger one of the largest ever oil leaks from a tanker and was still on fire as of Monday.
The Houthis have targeted several ships in the Red Sea over the last 10 months, a campaign which the Iran-backed group says is in support of Hamas in Gaza.
US military central command said late on Tuesday that the stricken tanker “threatens the possibility of a major environmental disaster”, and accused the Houthis of “reckless acts of terrorism”.
It said a salvage operation was “under way”, although it is not clear if salvage vessels have yet reached the Sounion.
On Monday, the EU’s military operation in the region said several fires were continuing to burn on the tanker’s main deck, though there were no visible signs that an oil spill was already occurring.
The Houthis – who have falsely claimed to only target Israeli, US and UK ships – attacked the Sounion with gunfire, before hitting it with three unidentified projectiles, UK Maritime Trade Operations (UKMTO) said last week. Its 25 crew members were rescued by a European warship.
The tanker was later attacked again, with footage released by the group showing Houthi militants boarding the ship and lighting fires on its deck.
The leader of the Houthis called the attack “brave and bold” in a recent address.
The US State Department has previously warned a spill from the Sounion could be almost four times as large as the Exxon Valdez disaster in 1989. That incident saw 2,100km (1,300 miles) of coastline contaminated after a tanker ran aground off Alaska.
The Houthis have continued to target crude oil tankers in the Red Sea in recent days.
On Monday, US military command said two vessels carrying oil were hit with ballistic missiles and a drone, including the Saudi-owned and flagged MV Amjad, which is said to be carrying around two million barrels of oil.
A US-led military operation has carried out strikes in Yemen, where the Houthis control much of the country, in an attempt to disrupt its ability to strike vessels passing through one of the world’s busiest shipping lanes.