While a major spill has yet to occur, the incident threatens to become one of the worst yet in the Houthi campaign -- in solidarity with Palestinians suffering under Israel's assault on Gaza -- that has disrupted the $1 trillion in goods that pass through the Red Sea each year. It also has halted some aid shipments to conflict-ravaged Sudan and Yemen.

“The private companies responsible for the salvage operation have concluded that the conditions were not met to conduct the towing operation and that it was not safe to proceed,” the EU’s Operation Aspides mission said, without elaborating. “Alternative solutions are now being explored by the private companies.”

The safety issue could be the fire burning aboard the vessel. Satellite images from Planet Labs PBC taken Tuesday afternoon and analyzed by the AP showed the Sounion still ablaze.

The US State Department has warned that a spill from the Sounion could be “four times the size of the Exxon Valdez disaster” in 1989 off Alaska.

Meanwhile, there's the threat of attacks by the Houthis, who on Monday targeted two other oil tankers travelling through the Red Sea. The Houthis have suggested they'll allow a salvage operation to take place, but critics say the rebels have used the threat of an environmental disaster previously involving another oil tanker off Yemen to extract concessions from the international community.

The Houthis initially attacked the Greek-flagged Sounion tanker on Aug. 21 with small arms fire, projectiles and a drone boat. A French destroyer operating as part of Operation Aspides rescued its crew of 25 Filipinos and Russians, as well as four private security personnel, after they abandoned the vessel and took them to nearby Djibouti.

Last week, the Houthis released footage showing they planted explosives on board the Sounion and ignited them in a propaganda video, something the rebels have done before in their campaign.

The Houthis have targeted more than 80 merchant vessels with missiles and drones since Israel's war on Gaza started in October. They seized one vessel and sank two in the campaign that has also killed four sailors. Other missiles and drones have either been intercepted by a US-led coalition in the Red Sea or failed to reach their targets, which have included Western military vessels as well.

The rebels maintain that they target ships linked to Israel, the US or the UK to force an end to Israel’s 11-month assault on Gaza. However, many of the ships attacked have little or no connection to the conflict, including some bound for Iran.

There are no American vessels known to be in the Red Sea at the moment as the EU mission has taken charge after the Sounion attack. A US defence official, who spoke to the AP on condition of anonymity to discuss information not made public, said the American military has not been asked and has no role in the cleanup or the towing of the Sounion.

The USS Dwight D. Eisenhower recently served a monthslong deployment in the Red Sea, facing the most intense, continuous combat the US Navy has seen since World War II while fighting against the Houthis.

The US aircraft carrier USS Theodore Roosevelt, along with its carrier groups, are in the Gulf of Oman to counter a threatened Iranian retaliation against Israel over the assassination of Hamas leader Ismail Haniyeh in Tehran. Satellite pictures and a report Tuesday from the US Navy Institute suggest the USS Abraham Lincoln and its strike group, once with the Roosevelt, has moved into the Gulf of Aden.

However, the US has continued a campaign of airstrikes targeting the Houthis. A strike Tuesday destroyed a Houthi missile system, the US military's Central Command said.

Matthew Bey, a senior analyst at the RANE Group, warned that the Houthis' attacks likely will continue until there's a ceasefire in Gaza.

Even then, there's a risk that the rebels continue the attacks.

*This story was edited by Ahram Online.