By Barbara Starr

U.S. intelligence and the Pentagon have begun assembling preliminary information about potential targets and militant personnel in Libya that could be struck if President Barack Obama ordered such action.

A senior U.S. official, who declined to be identified because of the sensitive nature of the information, confirmed details to CNN, noting the United States would likely seek cooperation from Libya before launching any military strike.

Some of the details were first reported by the New York Times.

The stepped up effort is in response to the September 11 attack on the U.S. consulate in Benghazi that killed Ambassador Christopher Stevens and three other Americans.

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U.S. intelligence has said it believes the attack was "a deliberate and organized terrorist assault carried out by extremists" affiliated or sympathetic with al Qaeda.

CNN reported previously that U.S. drones have been collecting intelligence in eastern Libya for weeks, and that American intelligence agencies are eavesdropping and intercepting suspected insurgent communications.

The official offered repeated caution about the effort. While he acknowledged that "options are being teed up," he said "don't think that a final list of who was involved is solid."

He said any early list of targets or personnel is part of standard target planning and is "highly pre-decisional," noting that the president would have to decide whether to launch a strike.

The official repeatedly noted the standard job of the intelligence community and the military is to prepare options for the president if he asks for them, which he has not.

The current effort involves assembling so-called "target packages." A target package includes the intelligence matched to a specific site earmarked for a potential strike.

It also includes intelligence justifying a potential strike against any enemy personnel being targeted and a specific calculation on how civilian casualties would be avoided.

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