Blair told The Sun newspaper that he had been ready to quit if he was defeated in last month's vote authorising military action by rebel members of parliament in his own Labour party.
"In the end, it is a decision you put the whole of the premiership on the line for," he told Britain's top-selling tabloid.
"It was always possible that you could be in that situation. But the point is that some people are going to die as a result of your decision," he said.
"In the end if you lose your premiership, well you lose it. But at least you lose it on the basis of something that you believe in," he said.