Tony Blair has backed "regime change" in Iran and Syria in an interview to mark the tenth anniversary of the 9/11 attacks.
The former prime minister told The Times he blames "external factors" such as Iran for prolonging the conflicts in Afghanistan and Iraq for so long.
He also suggests Iran's threat to the area remains "immense" and that the West must be prepared to use force if Tehran pursues its nuclear ambitions.
"Regime change in Tehran would immediately make me significantly more optimistic about the whole of the region," Mr Blair said.
But he insisted he was not advocating military action - instead, he wants countries to use determination to face down the threat.
"If Iran were to acquire nuclear weapons capability it would destabilise the region very, very badly," he said.
"They continue to support groups that are engaged with terrorism and the forces of reaction.
"In Iraq one of the main problems has been the continued intervention of Iran and likewise in Afghanistan," he added.
Reflecting on the invasions of Afghanistan and Iraq, Mr Blair admitted he mistakenly expected the interventions to be relatively short.
He said while there were not many extremists, a "worryingly large" number of people bought into the ideology.
"We are a long way from getting out of this," he added.
He made the remarks days before the tenth anniversary of the 2001 terror attacks which saw two hijacked planes hit the Twin Towers in New York.
Another plane hit the Pentagon, while a fourth came down in a field in Pennsylvania.
Sky's foreign affairs editor Tim Marshall said: "(Mr Blair) says the threat is bigger and deeper now than it was in 2001 in the weeks after 9/11.
"That's a debatable point. Some people say that the jihadist ideology is sinking. Other people don't accept that and say the franchise puts us in more danger than ever.
"(Mr Blair and Mr Sarkozy also) believe that this 'left' and 'right' (split in politics) is old-fashioned."
Mr Blair is expected to spend Sunday in the Middle East due to his role representing the Quartet - the US, the European Union, the United Nations and Russia.
Britain's prime minister at the time of the attacks, Mr Blair was in Brighton at the annual Trades Union Conference (TUC) when he first heard of the unfolding events.
On Syria, he said president Bashar al Assad was "not capable of reform" and his position is untenable.
"There is no process of change that leaves him intact," he told the newspaper.
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