Former British Prime Minister Tony Blair says the Islamic State group will be defeated only with a ground war involving Western troops.

Blair says air strikes alone will not defeat the militants. He said Tuesday that "you are going to have to go and wage a proper ground war," with British and American troops playing a supporting role.

Blair's decision to take Britain into the U.S.-led invasion of Iraq in 2003 remains deeply divisive, and Iraq is mired in violence. Blair is likely to be criticized in a long-delayed report on the war and its aftermath that will published in July.

At an event in London, Blair acknowledged the invading nations had underestimated the "forces of destabilization" that would emerge in Iraq after the toppling of dictator Saddam Hussein.