Laura Kuenssberg
BBC political editor

It has taken longer than anyone expected.

But the conclusions, reached with the weight of more than two million words, backed with evidence from thousands upon thousands of documents, are crystal clear, polite - but no doubt, completely damning - even if perhaps no real surprise.

There will be weeks of searching through the evidence that's been published for the first time today, so these first reflections may be reshaped in the days to come. But in these first hours, Sir John Chilcot's judgements seem careful, but bold and precise.

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Responding to questions from journalists, Mr Blair says passionately while gesticulating with his arms that some people talk "as if I don't care about the loss of life".

But he says: "I had to decide are more people going to suffer, are more people going to die if we leave this dictator in power."

Asked whether he would apologise to the families of the British servicemen and women who lost their lives, Mr Blair says: "I can look not just the families of this country, but the nation in the eye, and say I did not mislead this country. I made the decision in good faith on the information I had at the time, and I believe it is better we took that decision."

Mr Blair says: "The real threat is Islamist extremism and its ideology," adding that it must be confronted with "a combination of hard and soft power."  

He adds that extremism is "the scourge of our time" and that the UK needs to urgently put in a strategy to tackle it and an honest debate about the UK's role.  

Mr Blair says he will take questions after his statement.

In concluding, he acknowledges that many people will find it impossible to reconcile his decision.

"I hope future leaders can learn from mistakes I made... There will not be a day in my life when I don't relive and rethink what had happened."

Former Labour cabinet minister Tessa Jowell has said there was no "war plan" with then US president George W Bush and "no deception of the cabinet" in the run-up to the Iraq War. 

She said the Chilcot report showed there was no "falsification of intelligence", that "the attorney general's advice was in place and the cabinet wasn't misled".

She said she hoped the publication of Sir John's report gave "some comfort to the families who lost people they loved" but said it showed: "Not an illegal war, no deception of the cabinet and no question of there being a war plan with George Bush."

Mr Blair addresses the suggestion in the report that military action might have been necessary later. 

He argues that if the coalition had withdrawn the threat of action in 2003 it would have found it almost impossible to regroup its forces, and Saddam Hussein would have been in a strengthened position.

"Even if you disagreed with removing Sadaam in 2003, you should be thankful we are not dealing with him now," he says.

Mr Blair adds: "None of this excuses the mistakes we made, none of this excuses the failures."

Image source, AP

Memos sent by former UK prime minister Tony Blair to then US President George W Bush in the run-up to the Iraq War shine a light on the extent of the relationship between the two leaders.

The memos sent between 2001 and 2007 were released alongside Sir John Chilcot's report of his inquiry into the Iraq War., external

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Tony Blair has said that he takes "full responsibility" for the decisions that led to the UK's involvement in the 2003 Iraq War.

The former prime minister was giving his reaction the the publication of the long-awaited Chilcot report.

Mr Blair said he expressed "more sorrow, regret and apology" than people could ever know.

Mr Blair accepts "in hindsight" that the planning for war should have been different.

But he says: "If you knew the fact this dictator used chemical weapons... had continued to lie about them.. would you have wanted to take the risk of leaving him in place?"

BBC News security correspondent Gordon Corera writes: "The Iraq Inquiry, external by Sir John Chilcot presents a devastating picture of intelligence that is damning for both spies and the politicians.

"It is critical of MI6's collection and presentation of its sources; of the analysis by the wider intelligence community; of the way the Joint Intelligence Community allowed its material to be used and of the way in which politicians talked about intelligence to the public.

"The story of one particular MI6 agent, as told in the inquiry report, reveals much of what went wrong." 

Read more here.

"I knew it was an unpopular decision," Tony Blair says with a quavering voice.

"The political cost shrinks into complete insignificance compared to the human cost."  

"I did it because I thought it was right ", he adds, and because he believed the human cost "would be greater in the long run".

The reality, continues Mr Blair, is Britain had continually acted within the authority of the UN.

But Mr Blair says there came a point when he didn't have the option of delaying the decision to go to war - "I had to decide".

"I knew it was not a popular decision. I knew what its costs were politically... I did it because I thought it right and the human costs of leaving Saddam in power would be greater for us in the longer term".