The 2003 invasion of Iraq is not to blame for the violent insurgency now gripping the country, former UK prime minister Tony Blair has said.
Speaking to the BBC’s Andrew Marr, he said there would still be a “major problem” in the country even without the toppling of Saddam Hussein in 2003.
Mr Blair said the current crisis was a “regional” issue that “affects us all”.
And he warned against believing that if we “wash our hands of it and walk away, then the problems will be solved”.
“Even if you’d left Saddam in place in 2003, then when 2011 happened – and you had the Arab revolutions going through Tunisia and Libya and Yemen and Bahrain and Egypt and Syria – you would have still had a major problem in Iraq,” Mr Blair said.
“Indeed, you can see what happens when you leave the dictator in place, as has happened with Assad now. The problems don’t go away.
“So, one of the things I’m trying to say is – you know, we can rerun the debates about 2003 – and there are perfectly legitimate points on either side – but where we are now in 2014, we have to understand this is a regional problem, but it’s a problem that will affect us.”
Syria is three years into a civil war in which tens of thousands of people have died and millions more have been displaced.
In August last year, a chemical attack near the capital Damascus killed hundreds of people.
In August, UK MPs rejected the idea of air strikes against Syrian President Bashar al-Assad’s government to deter the use of chemical weapons.
Writing on his website, the former prime minister warned that every time the UK puts off action, “the action we will be forced to take will be ultimately greater”.
He said the current violence in Iraq was the “predictable and malign effect” of inaction in Syria.
“We have to liberate ourselves from the notion that ‘we’ have caused this,” he wrote. “We haven’t.”
He said the takeover of Mosul by Sunni insurgents was planned across the Syrian border.
“Where the extremists are fighting, they have to be countered hard, with force,” Mr Blair said.
The Sunni insurgents, from the Islamic State in Iraq and the Levant (ISIS), regard Iraq’s Shia majority as “infidels”.
After taking Mosul late on Monday, and then Saddam Hussein’s hometown of Tikrit, the Sunni militants have pressed south into the ethnically divided Diyala province.
On Friday, they battled against Shia fighters near Muqdadiya – just 50 miles (80km) from Baghdad’s city limits.
Reinforcements from both the Iraqi army and Shia militias have arrived in the city of Samarra, where fighters loyal to ISIS are trying to enter from the north.
Mr Blair also told the BBC that the UK and its allies had to “engage” and try to “shape” the situation in Iraq and Syria.
“If you talk to security services in France and Germany and the UK, they will tell you their single biggest worry today are returning Jihadist fighters, our own citizens, by the way, from Syria,” he said.
“So, we have to look at Syria and Iraq and the region in context. We have to understand what’s going on there and we have to engage”.
Civil war in Syria was “having its predictable and malign effect” and there was “no doubt that a major proximate cause of the takeover of Mosul by ISIS” was the situation in the country, Mr Blair said.
He said the operation in Mosul was planned and organised from Raqqa across the Syria border.
“The fighters were trained and battle-hardened in the Syrian war,” he said.
The 2003 invasion of Iraq by British and US forces, on the basis that it had “weapons of mass destruction”, has come back into focus as a result of the insurgency in the country.
The Iraq War has been the subject of several inquiries, including the Chilcot inquiry – which began in 2009 – into the UK’s participation in military action against Saddam Hussein and its aftermath.
Last month, the inquiry said details of the “gist” of talks between Tony Blair and former US president George Bush before the Iraq war are to be published.
Mr Blair has said he wants the Chilcot report to be published and he “resented” claims he was to blame for its slow progress.