Al-Qaeda chief Zawahiri urges 'lone-wolf' attacks on US
The leader of al-Qaeda has issued a message marking the 12th anniversary of the 11 September 2001 attacks.
In the audio message, Ayman al-Zawahiri talks of the need for small-scale attacks - and even a boycott - to damage the US economy.
The message may be seen as a sign of diminishing ambitions and a more realistic assessment of what al-Qaeda's central organisation can achieve.
Zawahiri's message also praised the bombings in Boston in April.
His message begins with a familiar claim that his organisation has the upper hand.
He says that the US has fled Iraq and Afghanistan in "defeat".
He goes on to emphasise the importance of so-called "lone-wolf", or small-scale attacks as part of al-Qaeda's strategy.
Such attacks, he argues, will have an economic impact above all.
"We must bleed America economically by provoking it, so that it continues its massive expenditures on security. America's weak spot is its economy, which began to totter from the drain of its military and security expenditure," he says.
Zawahiri advocates "continuing the drain of military and security expenditures so that we keep America in a state of tension and anticipation, [wondering] when and where the next blow will come".
"Keeping America in a state of tension and anticipation does not cost us anything but [organising] dispersed strikes here and there. In other words, just as we defeated it in a war of nerves in Somalia, Yemen, Iraq and Afghanistan, we must afflict it with a similar war in its own home.
"These dispersed strikes can be carried out by one brother, or a small number of brothers."
The emphasis on smaller-scale strikes may well be seen as an acknowledgement of a diminishing ability of al-Qaeda's central leadership to plan and carry out major, organised attacks of the type it managed in the past.
That shift is evident in Zawahiri calling on supporters to begin an economic boycott.
"We must explain to them that every dollar's worth of goods that we buy from America and her allies amounts to a bullet or shrapnel that kills a Muslim in Palestine or Afghanistan."
Most analysts believe that the al-Qaeda core in Pakistan has been severely damaged and this message appears to be an acknowledgement of that reality.
However, affiliates in other parts of the world - notably al-Qaeda in the Arabian Peninsula, based in Yemen - are said by government officials to remain a threat.
Zawahiri, who has historically tended to focus more on ideology and strategy, also spends a significant amount of the message talking about recent events in Egypt.
He says that the US was behind the "coup" against the Muslim Brotherhood.
He also criticises Mohammed Morsi, the deposed president who hails from the Muslim Brotherhood, saying he was not governing according to Islamic law and had committed to abide by security agreements with the US and Israel.
Zawahiri, whose background before joining al-Qaeda was in Egypt's Islamist movements, also emphasises his opposition to the Brotherhood's willingness to work through democratic politics.
He criticises other Islamist movements in places like Tunisia for coming to "an understanding with America".
The events in the Middle East have raised serious ideological challenges for al-Qaeda, with it appearing increasingly irrelevant amid signs that protests, people power and even democratic elections might be a more viable vehicle for change than the kind of violence that al-Qaeda espoused.
However, with the optimism of the past few years fading fast, Zawahiri appears to be hoping that al-Qaeda's ideology of rejecting democracy and promoting uncompromising violence might be able to gain more of a foothold.
Syria remains a key focus for international attention - including for al-Qaeda. Zawahiri warns Islamist opposition groups there not to come to any agreement with "secularists" who are also fighting the Assad regime.
"Let what happened in Egypt be a lesson to them," he says, before arguing that the jihadists groups need to unite in the region.
This may well be a reference to recent reports of splits and divisions, not just within Syrian jihadist groups but also with the Iraqi-based groups.