It is believed some of the most radical mullahs in the UK will attend a conference at Finsbury Park mosque in north London.
They are expected to argue that the attacks on America were justified because Muslims must defend themselves against armed aggression.
The conference will be co-chaired by Sheikh Abu Hamza al-Masri, a cleric at Finsbury Park mosque, who lost both hands and an eye fighting in Afghanistan during the Soviet occupation.
'Way forward'
Sheikh Omar Bakri Mohammed, whose al-Muhajiroun group wants to establish a worldwide Islamic state, will also be attending the event.
He said: "The conference is about remembering September 11 and looking at the outcomes and the likely causes of the problem.
"We will look at the way forward in order to prevent this happening again."
Other speakers include Yasser al-Siri, 40, an Egyptian-born dissident who was released from custody in July when extradition proceedings by the US were dropped.
In August, Sheikh Abu Hamza and Sheikh Omar Bakhri Mohammed addressed a rally in London's Trafalgar Square but only a few dozen supporters turned up.
The conference will also see the launch of the Islamic Council of Britain, which supports the implementation of Muslim Sharia law in Britain.