Some U.S. officials question response to Iran plot

These officials, while not disputing many facts of the case, say that if anything, the scheme reveals weaknesses in Iran's security agencies, and the increasingly fractured state of Iran's government as it faces intense international pressure.

They also questioned the wisdom of the White House strategy in using the affair to rapidly push for tougher sanctions on Tehran, increasing regional tensions.

"A lot of people basically feel really suspicious about this," one official said, questioning the White House's motivation "in ratcheting this thing up so quickly."

Like others, this official insisted on anonymity because he was not authorized to speak publicly.

A second U.S. official said he shared those concerns, and questioned whether new sanctions, especially unilateral U.S. ones, would have much more than a cosmetic effect on the already heavily sanctioned country.

The consensus view in the administration is that Iran's supreme leader, Ayatollah Ali Khamanei, probably knew of the alleged plot to kill Saudi Arabia's ambassador in Washington, while President Mahmoud Ahmadinejad did not.

But the skeptical officials said there is no hard evidence Khamanei knew or approved of the plan.

A criminal complaint unsealed this week charges an Iranian-American now in custody, Manssor Arbabsiar, and Gholam Shakuri, a reputed member of Iran's shadowy Quds Force, of conspiring to kill the ambassador, Adel al-Jubeir.