Filed at 6:41 p.m. ET
WASHINGTON (AP) -- U.S. counterterrorism officials believe al-Qaida is targeting oil interests in the Middle East, hitting one tanker off Yemen and failing in an attempt to attack a Saudi pipeline and a nearby port complex.
Saudi authorities reported foiling a planned terrorist attack on a major pipeline this summer, said a U.S. defense official, speaking on the condition of anonymity. Documents recovered during the war in Afghanistan also suggested al-Qaida was planning strikes on oil interests, another official said.
In addition, Yemeni officials acknowledged for the first time Wednesday that the French tanker Limburg was rammed by an explosives-laden boat on Oct. 6 off the coast of Yemen.
U.S. counterterrorism officials say they believe the attack was conducted by al-Qaida operatives.
Details of the Saudi plot were sketchy, but Saudi authorities are said to have made more than 20 arrests over the summer in connection with the planned strike.
The target was believed to have been the Ras Tanura oil terminal and refinery, as well as pipelines that serve it. Whether the plotters had the capability to knock such a large facility out of action is unclear.
The sprawling industrial complex, on the Persian Gulf, transfers 5 million barrels of oil to tankers a day, more than six percent of the 80 million barrels consumed daily worldwide.
``It's the single most important facility in the oil industry,'' said Roger Diwan, an energy market analyst with the Petroleum Finance Company in Washington. ``It's the vital artery for oil exports.''
A strike on a single tanker has a negligible economic effect, experts said. Pipeline bombings -- a frequent tactic of Colombian guerrillas -- are troublesome, but lines can be repaired. But a successful bombing of Ras Tanura could have far-reaching consequences, even if the complex was not shut down, experts said.
Fear of strikes on the oil industry could cause prices to rise, as suppliers worldwide take extra security precautions and insurance premiums go up, experts said.
Much of the Ras Tanura terminal's oil is bound for Asia, but plenty goes to Europe and the Americas, analysts said.
It is well-defended against both military and terrorist attack, Diwan said. It is extremely difficult to approach without being detected, he said.
``Ras Tanura is a vast complex,'' he said. ``It's very well-secured. It has redundant facilities. You put a bomb somewhere; it doesn't matter.''
Major bombings at multiple points would be necessary to even damage the complex, experts said.
But if Ras Tanura shut down for a significant period, oil shortages are a possibility, particularly if Iraqi oil also stopped flowing during a U.S. invasion, said Lowell Feld, an oil analyst at the Energy Information Administration, an independent arm of the Department of Energy.
Saudi Foreign Minister Prince Saud said last week that authorities had recently made several new arrests of al-Qaida operatives, but declined to go into detail.
U.S. counterterrorism officials believe attacks on oil interests are in line with recent promises by al-Qaida leaders to attack economic targets.
On Oct. 6, an audio tape of Osama bin Laden threatening such strikes aired on the pan-Arabic al-Jazeera network.
``By God, the youths of God are preparing for you things that would fill your hearts with terror and target your economic lifeline until you stop your oppression and aggression (against Muslims),'' bin Laden said. It is not known when the tape was made.
On Monday, a written statement attributed to bin Laden was given to al-Jazeera and appeared on some Web sites associated with Islamic extremists. U.S. officials aren't certain bin Laden wrote the statement, but it refers to the Yemen tanker strike.
``By exploding the oil tanker in Yemen, the holy warriors hit the umbilical cord and lifeline of the crusader community, reminding the enemy of the heavy cost of blood and the gravity of losses they will pay as a price for their continued aggression on our community and looting of our wealth,'' the statement says.
One crewman was killed in the tanker attack. Other recent attacks have also been attributed to al-Qaida and its operatives, including Saturday's bombing of a night club in Bali and last week's shooting of a U.S. Marine in Kuwait.
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Associated Press writer Pauline Jelinek contributed to this story.