ISMAILIA, Egypt — Efforts to dislodge the mammoth vessel blocking Egypt's Suez Canal proceeded Sunday, but it remained unclear when or how the Ever Given cargo carrier would break free from the muddy banks of one of the world's key waterways for global trade.

There were positive signs: Larger and heavier tugboats were on their way, and a full moon Sunday night bore the promise of a powerful tide to aid refloating efforts. Still, Egyptian authorities resolved to explore other options.

Egyptian President Abdel Fatah al-Sissi ordered preparations to be made for the unloading of the stranded Ever Given, the head of the Suez Canal Authority said Sunday.

Lt. Gen. Osama Rabie told Egyptian television that in case dredging and tugboat operations failed, officials were preparing for the "third scenario" of unloading containers in a bid to refloat the Ever Given. The canal has been blocked since Tuesday, leaving more than 300 ships waiting to pass through.

Unloading some of the towering ship's 18,000 containers would require special equipment, which is why the president authorized its acquisition even as dredging continued, Rabie said. So far, 27,000 cubic feet of sand have been removed from around the vessel to a depth of about 60 feet.

"His Excellency has ordered that we should not wait for the failure of the first and second scenarios to start thinking about implementing the third one," Rabie said.

Earlier, there had been hopes that the vessel could be freed overnight with the high tide, but "the tidal [conditions] didn't help re-floating #EverGiven tonight," canal services provider Leth Agencies tweeted early Sunday morning, adding that "dredgers will continue their work, tugs will assist in new attempts."

Two more tugboats were dispatched to the scene as well: the Italian-flagged Carlo Magno and the Dutch-flagged Alp Guard, which made it to the scene Sunday.

The refloating process was delayed again Sunday afternoon, with the company saying another effort was likely Monday evening, once the tide was high and the Carlo Magno had also arrived.

The 200,000-ton container ship, as long as the Empire State Building is tall, is costing billions of dollars in global trade every day. The fifth day of the salvage operation illustrated the technical and weather challenges facing the international team seeking to dislodge the Ever Given and stave off a global economic calamity.

Officials were hopeful on March 27 that the grounded ship in the Suez Canal could be freed by a rising tide brought on by the arrival of heavier tugboats. (Reuters)

Syria announced Saturday that it had begun rationing oil supplies, in particular diesel and gasoline, because of the canal blockage.

The Danish shipping giant Maersk said Sunday that it is continuing efforts to mitigate the situation, including rerouting 15 ships in a bid to keep cargo moving through the waterway.

“We have until now redirected 15 vessels where we deemed the delay of sailing around the Cape of Good Hope at the southern tip of Africa equal to the current delay of sailing to Suez and queuing,” the statement said. The African route adds weeks to the trip.

The company said it would consider rerouting more vessels Monday.

CNN reported Friday that a U.S. Navy team of dredging experts was expected to arrive as early as the weekend to assess the situation. As of Sunday, it was unclear whether any Navy personnel had reached the Suez or performed an assessment.

Bernhard Schulte Shipmanagement, which oversees the ship’s crew and maintenance, said in a statement that the salvage efforts began again at 2 p.m. Saturday, after “significant progress” was made to free the vessel’s rudder from the sand and mud. But by midnight, with at least 11 tugs on the job, it was clear that operations to remove thousands of tons of sediment from around the port side of the vessel’s bow would require more time and effort.

But as flotation attempts continued, industry experts debated whether the saga of the wedged ship may have been preventable, given years of warnings that the size of vessels using the waterway was growing to meet economic demand but risk assessments were not keeping pace.

“This is a big ship and a big problem, but it is not like we have not seen this coming,” Richard Meade, editor of the Lloyd’s List shipping journal, said on a recent podcast.

On Sunday, six more ships entered the canal, bringing the number of vessels trapped in the massive maritime congestion to 327, according to Leth Agencies.

In addition to the delays, shipping companies will face higher insurance costs. Only 1 in every 10 ships surrounding the stranded Ever Given has adequate insurance to cover mounting disruption costs, a Lloyd’s List analysis indicated, leading to further concerns about the financial effect of the standstill, which will probably affect different businesses in myriad ways.

According to the report, an estimated 90 percent of nearby ships will be unlikely to claim for “sizeable out-of-pocket expenses” incurred amid the chaos, which has forced hundreds to consider alternate routes, led to port and transit delays and disrupted the oil trade.

Experts have warned that unloading containers from the Ever Given to lighten the vessel could take days or even weeks, because doing so requires the use of extra-tall cranes and specialized helicopters. Such an effort would be extremely costly, and it’s not clear who would shoulder the expense.

On Saturday, Egyptian Prime Minister Mostafa Madbouly expressed appreciation for the offer from foreign allies to help free the ship.

 The salvage effort, led by an Egyptian, Dutch and German team and including tugs from Italy and the Netherlands, has become a genuinely international operation, mirroring the global shipping industry and the Ever Given itself. The ship is owned by a Japanese company and operated by a Taiwanese firm, its crew is Indian, and it sails under a Panamanian flag.

Hassan reported from London. Heba Farouk Mahfouz in Cairo and Antonia Noori Farzan and Ruby Mellen in Washington contributed to this report.