As the US blames Iran for plotting to kill the Saudi Arabia ambassador for Washington, a Chatham House expert casts doubt over the allegations.

Questions raised over Iran's role in assassination plot. (Reuters)

Much has been made of the antagonism between Saudi Arabia and Iran as a potential motivation for the alleged bomb plot. However Richard Dalton, associate fellow at the Chatham House Middle East and North Africa programme, tells Channel 4 News he is not convinced.

"It's highly doubtful that as an act of state policy, the Iranians would have wanted to assassinate the Saudi Arabian ambassador," he said.

"There have been tensions between the two countries, but not in the military sense. Neither wants to be in a war with the other. The Saudis have been a principal opponent of Iranian influence in Iraq for example, but they are regional rivals, rather than military.

"And there's obviously no interest for Iran in cementing an already established relationship between Saudi Arabia and the US."

Mr Dalton says an attempt by two freelance Iranians can't be ruled out, "or that the whole this has been made up to demonise Iran."

There's obviously no interest for Iran in cementing an already established relationship between Saudi Arabia and the US. Richard Dalton, Chatham House

Iranian policy is 'defensive'

An analysis of Iran's previous policy shows that this kind of attack is unlikely, says Mr Dalton.

Even Kenneth Pollack, a former CIA and National Security Council analyst, who now heads the Saban Centre for Middle East policy in Washington, said that the attack would "be a first for the Quds Force" when he first heard the US allegations.

"I do want to hear more about what evidence (the US authorities) have and why they believe" that the Quds Force was involved, he said.

"Iranian policy is primarily defensive," Mr Dalton told Channel 4 News. "They are subject to attacks from Israel and the US. The US has long wanted a regime change within Iran and they (Iran) show defiance in response to that, but an act of this kind does not seem to me to fit in to their kind of policy."

In addition, the US allegations are unlikely to be believed among people the Middle East, said Mr Dalton, adding: "they are likely to say, who would benefit?"

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