The terrorist bombing of a French oil tanker off Yemen and a foiled attack on a Saudi oil complex has American counterterrorism officials worried that Al Qaeda is targeting petroleum interests in the Middle East.

Recent statements attributed to senior Al Qaeda leaders also suggest economic interests, including oil, are being considered for strikes. This would be a new tactic for the terrorist network, which has previously focused its attacks in the Middle East on the U.S. military and diplomatic presence there.

Saudi authorities reported averting an attack on a major pipeline and oil terminal complex this summer, said a U.S. defense official, speaking on the condition of anonymity.

Documents recovered during the war in Afghanistan also suggested Al Qaeda was planning strikes on oil interests, another defense official said.

On Wednesday, Yemeni officials also acknowledged an explosives-laden boat crashed into the French tanker Limburg on Oct. 6 off the coast of Yemen, killing one crewman. U.S. counterterrorism officials say they believe the attack was conducted by Al Qaeda 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, daily transfers 5 million barrels of oil to tankers, more than 6 percent of the 76 million barrels produced worldwide each day.

"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 guerillas — 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.

"Ras Tanura is a vast complex,'' said Diwan. "It's very well-secured. It has redundant facilities. You put a bomb somewhere; it doesn't matter.'' It also is extremely difficult to approach without being detected, he said.

Experts said major bombings at multiple points would be necessary to even damage the complex.

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, a statistical agency in the Department of Energy.

U.S. counterterrorism officials see attacks on oil interests in line with recent promises by Al Qaeda leaders to attack economic targets. And Saudi Foreign Minister Prince Saud said last week that authorities had recently made several new arrests of Al Qaeda operatives, but declined to go into detail.

On Oct. 6, an audio tape of Usama bin Laden, aired on the pan-Arabic al-Jazeera network, threatened strikes that "target your economic lifeline.'' The voice is believed, indeed, to be bin Laden's, but it is not known when the recording was made.

On Monday, a written statement, attributed to bin Laden, was given to al-Jazeera and appeared on some Internet sites associated with Islamic extremists. "By exploding the oil tanker in Yemen,'' it said, "the holy warriors hit the umbilical cord and lifeline of the crusader community.''

U.S. officials aren't certain bin Laden wrote it.