US officials acknowledge the alleged plot by Iran to assassinate Saudi Arabia's top diplomat in Washington sounds like a far-fetched Hollywood script, but insist it is a case of truth being stranger than fiction.
Many Western experts on Iran remain sceptical, however. They say Washington has yet to explain Tehran's motive for hatching such an inflammatory plot that, if successful, would have brought dire retribution.
"I'm doubtful about this because it doesn't fit with Iran's modus operandi or its foreign policy," a European former ambassador to Iran, said. "Why would Iran take such a high-level risk in killing a Saudi when that would simply drive up tensions in the region," the envoy, who requested anonymity, said in a telephone interview.
"And above all, why do it in America, thus exacerbating the problems Iran already has with a virulent enemy?"
But last night, US President Barack Obama said the US can support all the allegations of an alleged assassination plot against a Saudi Arabian diplomat and show the world that it was reckless behaviour on the part of the Iranian government. There will not be a dispute over what happened, Mr Obama told a White House news conference. Two men, including a member of Iran's Quds Force special foreign actions unit, were charged in New York federal court with conspiring to kill the Saudi ambassador to Washington. People in the Iranian government "were aware of this plot," Mr Obama said. "There has to be accountability." He said that one of the suspects was an individual of Iranian-American descent who had "direct links" to Tehran and was paid by Iran.
Iran is accused of planning to kill Saudi's US ambassador, Adel Al Jubeir, in a Washington restaurant, using a dodgy Iranian-American former used car dealer and a Mexican drugs cartel. Tehran yesterday rejected the charges as a "pathetic and conspiratorial US fabrication".
Unanswered is why Iran's sophisticated Quds force, which allegedly planned Mr Al Jubeir's murder, would use an Iranian-American with a reported criminal record for what would have been its boldest ever operation.
Why, too, would the Quds force believe that a Mexican drug cartel would be prepared to carry out a bomb attack in Washington? And given that the US has warned it is holding Iran accountable, what evidence is there that orders for the elaborate, alleged plot came directly from the upper echelons of the Iranian regime?
Those less sceptical of Washington's intentions ask in turn why the Obama administration would want to fabricate such accusations against Iran.
The Quds force is the 5,000-strong external operations unit of Iran's 150,000-member Republican Guard. Al Quds means Jerusalem in Arabic.
The secretive force has long been operational in Lebanon and, more recently, is said to be active in Syria, Iraq and Afghanistan. But a venture on US soil would be a first.
Iran has not carried out a political murder in the US since 1980 when an African-American convert to Islam, Daoud Salahuddin, killed the former press attaché at the Iranian embassy in a Washington suburb. The assassin was understood to have operated on his own initiative, although Iran gave him sanctuary.
Robert Baer, a former CIA agent, expressed his doubts about the alleged plot against Mr Al Jubeir in blunt terms. "This stinks to holy hell. The Quds force are very good. They don't sit down with people they don't know and make a plot," he told The Guardian.
The assassination plot suspects are Manssuor Arbabsiar, 56, arrested on September 29 in New York, and Gholam Shakuri, said to be a member of the Quds force.
Gary Sick, a scholar at the Middle East Institute at Columbia University in New York, found the plot allegations "very hard to believe". If true, the plot "departs from all known Iranian policies and procedures," Mr Sick, who monitored Iran for the US National Security Council during the 1979 Iranian revolution, wrote on his blog.
"Perhaps this operation is just as it appears," he added. "But at a minimum, both the [US] public and the Congress should demand more evidence before taking any rash or irreversible action."
US officials attempted to answer the sceptics' questions in off-the-record briefings to leading American media yesterday. Unnamed law enforcement officers attributed the amateurish nature of the plot to Iran's relative inexperience in carrying out covert operations in the US and Mexico.
They argued that a Mexican drug cartel would give Iran "deniability" while serving as a useful proxy in the US where the Iranians do not have an infrastructure. And, they added, the Iranian regime is under pressure at home and abroad, leading it to engage in riskier behaviour.
The officials said they believed Iran hoped the attack would be blamed on Al Qaeda.
Even if the US charges are true, analysts in Iran doubted that President Mahmoud Ahmadinejad knew of the plot, given that the Revolutionary Guard has withdrawn its support for him. The force has sided with his hardline clerical opponents in a bitter and protracted power struggle.
Among other things, opponents of the populist president accuse him of wanting to mend ties with the US because he knows it would go down well with Iran's young electorate. This has led to suspicions that the outlandish assassination plot was orchestrated by the Revolutionary Guard to torpedo any possible covert attempt by Mr Ahmadinejad to mend ties with the "Great Satan" America. Under that scenario, the plot was meant to be discovered by US intelligence.
The Quds Force and Revolutionary Guard are loyal to Iran's supreme leader, Ayatollah Ali Khamenei, who, despite his lurid anti-American rhetoric, is a cautious pragmatist. He knows his regime cannot afford a war against the US. It is also unlikely he would back any action that could see Iran slapped with new economic sanctions, Iran experts said.
For those reasons, some in Tehran speculate that the assassination plot, if genuine, may have been engineered by elements in the Iranian regime who wanted to hurt the ayatollah.
But the European former ambassador to Iran said it was "nonsense" to suggest that the risky plot had anything to do with the antagonism between Mr Ahmadinejad and Iran's supreme leader.