Osama bin Laden pondered the merits of US television news channels as he considered how to extract the best propaganda benefit from the tenth anniversary of 9/11 last year, and concluded that CBS was "close to being unbiased".

But an American-born media adviser for al-Qaeda warned Bin Laden to beware of the broadcasters' "cunning methods" as he described Fox News as a channel in the "abyss" that should "die in anger", CNN as too close to the US government and MSNBC as questionable after it fired one of its most prominent presenters, Keith Olbermann.

In a memorandum made public by the US military's Combating Terrorism Center on Thursday, Bin Laden asked for advice on exploiting the anniversary of the 9/11 attacks.

"We need to benefit from this event and get our messages to the Muslims and celebrate the victory that they achieved. We need to restore their confidence in their nation and motivate them. We should also present our just cause to the world, especially to the European people," he said.

Bin Laden suggested contacting Al-Jazeera.

"You can point out to them that this way they will be showing the other opinion," he said.

But he also wondered if it would be good to work with an American channel, suggesting CBS as "close to being unbiased". Bin Laden added that the organisation should approach a British journalist, Robert Fisk of the Independent, and other reporters to press home the message that the major powers would be better concentrating on climate change than pursuing al-Qaida. He wrote:

"This is a chance to explain our motives for continuing the war. The wise people would tell you to give people their rights in order to be able to focus on other vital issues such as global warming. They have the option to stop the war, but we do not have any option, except to defend our nation. This is a conflict between the biggest cultures in the world at a time when the climate is changing rapidly."

A US-born al-Qaida spokesman, Adam Gadahn, wrote back to Bin Laden laying the merits or otherwise of using US news stations to mark the "Manhattan battle" as it is referred to in the memo.

Fox News is dismissed because it "falls into the abyss as you know, and lacks neutrality too".

"I used to think that MSNBC channel may be good and neutral a bit, but is has lately fired two of the most famous journalists – Keith Olbermann and Octavia Nasser the Lebanese," wrote Gadahn.

In fact, Nasser was sacked from CNN after she sent a tweet mourning the death of a Hezbollah leader. Olbermann was dismissed for making financial donations to Democratic party politicians.

CNN is questioned, although its Arabic "version brings good and detailed reports".

"As for the neutrality of CNN in English, it seems to be in cooperation with the government more than the others (except Fox News of course)," he said.

Gadhan describes ABC as "all right":

"Actually it could be one of the best channels, as far as we are concerned. It is interested in al-Qaida issues, particularly the journalist Brian Ross, who is specialised in terrorism. The channel is still proud for its interview with the shaykh (Bin Laden)," he said. "CBS channel was mentioned by the shaykh. I see that it is like the other channels, but it has a famous programme (60 Minutes) that has some popularity and a good reputation for its long broadcasting time. Only god knows the reality, as I am not really in a position to do so."

The merits and shortcomings of other major US broadcasters are considered before Gadahn decided he couldn't make his mind up and worried that al-Qaida's message may come under critical scrutiny. He wrote:

"In conclusion, we can say that there is no single channel that we could rely on for our messages. I may ignore them, and even the channel that broadcast them, probably it would distort them somehow. This is accomplished by bringing analysts and experts that would interpret its meaning in the way they want it to be. Or they may ignore the message and conduct a smearing of the individuals, to the end of the list of what you know about their cunning methods." "In general, and no matter what material we send, I suggest that we should distribute it to more than one channel, so that there will be healthy competition between the channels in broadcasting the material, so that no other channel takes the lead. It should be sent for example to ABC, CBS, NBC, and CNN and maybe PBS and VOA. As for Fox News, let her die in her anger."

Gadahn also mentions sending "special media material" on the 9/11 anniversary to a number of newspaper journalists around the world, including Fisk. The intent, he said, is to "show the fairness of our case to the whole world and the European peoples in particular".

As it turned out, the advice was not required. Bin Laden was killed four months before the anniversary.