There were at least two jihadist operations in 2013 on the canal -- 120 miles long and 900 yards wide, most of which is vulnerable to attack.
No serious attacks have been reported since then but a study by the Combating Terrorism Center at the U.S. Military Academy warns the military-led government "appears increasingly incapable" of curbing such strikes and that "ships in the canal risk future attacks."
"There is concern that militants could successfully disrupt shipments through the Suez Canal, such as sinking a large vessel and blocking the canal for a period of time," the report, written by Middle East analyst Stephen Starr, concluded.
Egypt is not a major energy exporter but it earns $5 billion a year in transit fees from the canal, which links the Mediterranean Sea to the Red Sea, and beyond that, to the Arabian Sea and Indian Ocean. Losing that would be a major economic setback.
In a wider context, Egypt plays a vital role in international energy markets through the canal and the 200-mile SUMED pipeline that parallels the waterway from Port Suez in the south to terminals on the Mediterranean coast.
Tankers carrying 2.2 million barrels of crude oil and liquefied natural gas, or LNG, from the Persian Gulf move northward through the canal every day en route to Europe and the United States.
That's 7 percent of the world's oil supplies and 12 percent of the global LNG traffic.
SUMED -- for Suez to the Mediterranean -- carries around 1.7 million barrels of oil per day. It's used as an alternative for western-bound cargoes too big to transit by ship, or by Very Large Crude Carriers, or VLCCs, that need to lighten their loads so they can navigate the waterway.
Disruption of the supply routes would cause considerable economic distress, particularly in Europe. A shutdown would add about 2,700 miles of transit from Saudi Arabia to the United States around the Cape of Good Hope, pushing up shipping costs.
In addition to the energy traffic, more than 1,500 container ships bound for Europe and Asia passed through the canal in the second quarter of 2013, Egyptian statistics indicate.
The canal, with Sinai on its eastern bank and the Nile Delta to the west, was closed during the 1967 war with Israel. The Egyptian military shut it down during the 1956 Suez Crisis by scuttling 40 ships, blocking it for six months.
The Chinese-owned, Panamanian-flagged container ship Cosco Asia was attacked Aug. 31 with rocket-propelled grenades in the canal's northern Qantara sector. It suffered no serious damage.
The Al Furqan Brigades, one of the jihadist groups operating in Sinai, claimed responsibility.
It warned it would unleash further attacks on the canal because "it has become a safe passageway for the Crusader aircraft carriers to strike the Muslims, and it is the artery of commerce of the nations of unbelievers and tyranny."
The group had claimed an earlier RPG strike on a ship July 29.
The CTC report noted that "while security in ... Sinai Peninsula remains transient and the Egyptian state appears unable to stamp out militant activity in the Sinai, terrorist groups would have to employ new tactics to sink vessels if their goal was to block the canal for any period of time.
"Yet such tactics are not beyond their reach, and previous incidents of maritime terrorism could serve as their guide."
These include suicide bombers using small craft packed with explosives to ram ships, like al-Qaida's October 2000 suicide attack on the USS Cole in Yemen's Aden harbor, and on the French tanker Limburg off Yemen two years later.
Neither vessel was sunk but Starr observed that even if militants "failed to sink a major vessel, a waterborne suicide bomb attack on an LNG or oil tanker, or cruise or container ship ... would have immediate effects on the use of the Suez as a major shipping route... ."
"The threat of ... operations that sink a major vessel and thus block the canal ... is a real one."
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