LONDON - Former British prime minister Tony Blair defended the 2003 US-led invasion of Iraq on Friday, saying the Sept. 11 attacks on the United States meant Saddam Hussein had to be disarmed or removed. The al-Qaeda strikes against US cities had transformed the global security picture, raising the risk that militants could kill even more people if weapons of mass destruction (WMD) from a rogue state were to fall into their hands, Blair said. Facing the first official public grilling on why he sent 45,000 British troops to war in Iraq, Blair batted away questions about the legality of the invasion but admitted for the first time there had been mistakes in the post-war planning. The decision to go to war was the most controversial episode of Blair's 10-year premiership, provoking huge protests, divisions within his Labour Party and accusations he had deceived the public about the reasons for invasion. "This isn't about a lie, or a conspiracy, or a deceit, or a deception, this is a decision," said Blair, who initially looked nervous but grew more confident as the hearing went on. "And the decision I had to take was, given Saddam's history, given his use of chemical weapons, given the over 1 million people whose deaths he caused, given 10 years of breaking U.N. resolutions, could we take the risk of this man reconstituting his weapons programme? "I believed ... that we were right not to run that risk," added Blair, saying he was convinced even now that Saddam was intent on restarting his WMD programme even though no such weapons have ever been found. The Iraq war sapped support for Blair and his Labour Party and the issue still provokes deep public anger, seven years after the invasion to topple Saddam and almost three years after Blair handed over to Gordon Brown. Commentators say the current public inquiry could damage Labour before an election due by June, with the party trailing in opinion polls after 13 years in power. Under close questioning from the five-member panel, Blair, 56, was unrepentant over the stand he took with then U.S. President George W. Bush. Dressed in a dark blue suit and red tie, Blair began by explaining how his and the US view of Iraq dramatically changed after the Sept. 11, 2001 al- Qaeda attacks on the United States. No evidence has emerged to link Iraq with 9/11, but Blair said the attacks on the United States had changed the "calculus of risk".