Tony Blair says he's sorry for Iraq war 'mistakes'

"I can say that I apologize for the fact that the intelligence we received was wrong because, even though he had used chemical weapons extensively against his own people, against others, the program in the form that we thought it was did not exist in the way that we thought," Blair said in an exclusive interview on CNN's Fareed Zakaria GPS that airs Sunday.

Blair was referring to the claim that Saddam's regime possessed weapons of mass destruction, which was used by the U.S. and British governments to justify launching the invasion. But the intelligence reports the claim was based on turned out to be false.

The ensuing war and dismantling of Saddam's government plunged Iraq into chaos, resulting in years of deadly sectarian violence and the rise of al Qaeda in Iraq, a precursor of ISIS. Tens of thousands of Iraqis, more than 4,000 U.S. troops and 179 British service members were killed in the lengthy conflict.

As the most high-profile foreign ally of former U.S. President George W. Bush in the Iraq invasion, Blair has found his legacy overshadowed by the war, with questions and criticism following him wherever he goes.

The consequences of Bush's decision to to take America into Iraq has repeatedly reared its head this year among candidates vying for the 2016 Republican presidential nomination.

'I find it hard to apologize for removing Saddam'

Blair told Zakaria that besides the flawed Iraq intelligence, he also apologizes "for some of the mistakes in planning and, certainly, our mistake in our understanding of what would happen once you removed the regime."

But he stopped short of a full apology for the war.

"I find it hard to apologize for removing Saddam. I think, even from today in 2015, it is better that he's not there than that he is there," Blair said.

Saddam was notorious for his ruthless oppression of Iraqi citizens during more than three decades of dictatorship. He launched ruinous wars against neighbors Iran and Kuwait, and used chemical weapons against the Kurds in northern Iraq.

But present day Iraq is still under heavy strain from sectarian tensions and is struggling to deal with the threat of ISIS, the Sunni Muslim extremist group that has imposed its brutal rule on significant parts of the north and west of the country.

Admits partial responsibility for Daesh (ISIS) rise

Blair acknowledged to Zakaria that there are "elements of truth" in the view that the 2003 invasion of Iraq was the principle cause of the rise of Daesh.

"Of course, you can't say that those of us who removed Saddam in 2003 bear no responsibility for the situation in 2015," he said. "But it's important also to realize, one, that the Arab Spring which began in 2011 would also have had its impact on Iraq today, and two, ISIS actually came to prominence from a base in Syria and not in Iraq."

More broadly, Blair said, the policy debate on Western intervention remains inconclusive.

"We have tried intervention and putting down troops in Iraq; we've tried intervention without putting in troops in Libya; and we've tried no intervention at all but demanding regime change in Syria," he said. "It's not clear to me that, even if our policy did not work, subsequent policies have worked better."

Asked by Zakaria how he feels about being branded a "war criminal" for his decision to go into Iraq, Blair said he did what he thought was right at the time.

"Now, whether it's right or not, that's for -- everyone can have their judgment about that," he said.

Blair's interview with Zakaria comes ahead of a special program, "Long Road to Hell: America in Iraq," that premieres on CNN and CNN International on Monday at 9 p.m., ET.