Former British prime minister Tony Blair has described radical Islam as the greatest threat facing the world.
In an interview with the BBC to mark the publication of his memoirs, the former British prime minister said radical Islamists believed that whatever was done in the name of their cause was justified - including the use of chemical, biological or nuclear weapons.
Mr Blair, who led Britain into war in Afghanistan and Iraq, said the aim of al Qaeda in Iraq was "not to get American troops out of Baghdad [but] to destabilise a government the people of Iraq have voted for".
Iran was one of the biggest state sponsors of radical Islam, he said, and had to be prevented by any means from developing a nuclear weapon.
He said he was not advocating military action but simply saying no option could be taken off the table.
Mr Blair said he agonised over how to respond to radical Islam and still had doubts that he was right.
These are really difficult issues, he said, but added: "This extremism is so deep that in the end they have to know that they're facing a stronger will than theirs."