A long letter purportedly from Osama bin Laden's deputy, made public this week by the US, has been interpreted by some as a fundamental shift of strategy by the leadership of al-Qaeda. But it has also generated debate among experts about whether the letter is genuine - and, if it is, whether the US has mistakenly identified its intended recipient.
The US said the letter was from Ayman al-Zawahiri, al-Qaeda's number two, who is apparently holed up in the tribal areas of Pakistan. It said it was sent to Abu Musab al-Zarqawi, Jordanian-born head of a high- profile terror group called al-Qaeda in Iraq.
In a report to clients, Aegis Defence Services, a London-based consultancy, argued that the letter, addressed to Abu Musab, had actually been sent to Abu Musab al-Suri, also known as Mustafa Setmarian Nasar, a Syrian who acted as an intermediary for al-Qaeda in Europe during the 1990s and whose whereabouts were unknown.
The letter's respectful tone, coupled with a reference to Mr Zarqawi in the third person - "if by chance you are going to Fallujah, send greetings to Abu Musab al-Zarqawi" - suggested it was directed to a more intimate confidant than Mr Zarqawi.
A statement from Abu Maysara Iraqi, who claims to be aspokesman for the Zarqawi group, was carried on several Islamic websites on Thursday saying the US fabricated the letter.
Stephen Ulph, an analyst at the US-based Jamestown Foundation, said the letter presented a number of problems. There had been no clarification as to how it was intercepted and no independent corroboration of its authenticity. He also found it remarkable that a letter between two al-Qaeda leaders should spell out strategy in such an explanatory way, as if these basic details were the subject of doubt.
A spokesman for the Director of National Intelligence, which released the letter on Tuesday, said it "had been looked at by multiple agencies over a protracted period of time". There was "strong consensus as to its authenticity".
Taken at face value, the letter provides fascinating insights. It repeatedly refers to the author's isolation and his lack of knowledge of the situation in Iraq. Written on July 9, it makes no mention of the London bombings two days earlier.
According to Dominic Armstrong of Aegis, the letter contains the first acknowledgement from al-Qaeda that it is important to capture the support of the Muslim public, theologians and thinkers and that this cannot be taken for granted.
The letter questions the impact of some needlessly gruesome actions, such as the beheading of hostages and attacks on Shia Muslims, which it says could lift the burden on US forces.
However, some experts said the letter was consistent with what Mr Zawahiri had said in the past. "They've always avoided conflict and any public criticism of other sects or other Muslim schools or Muslim groups," said Saad al-Faguih, a London-based Saudi Islamist dissident. "And Zawahiri is the most political and the most calculating [among al-Qaeda leaders]."
