Asked about Saddam's sentence at his monthly press conference, Blair noted that Britain opposed the death penalty "whether it's Saddam or anyone else."
But he said the trial "gives us a chance to see again what the past in Iraq was, the brutality, the tyranny, the hundreds of thousands of people he killed, the wars."
Blair said the trial "also then helps point the way to the only future" the Iraqi people want: "a nonsectarian Iraq in which people from different communities live together and decide their future through democracy. I don't underestimate for a single instant the difficulties involved in achieving that, but it's a battle worth fighting."
In a testy exchange with a television journalist who interrupted him several times, Blair referred repeatedly to the statement Foreign Secretary Margaret Beckett issued after the verdict on Sunday. She welcomed "that Saddam Hussein and the other defendants have faced justice" but made no comment on the capital sentence.
The prime minister appeared uncomfortable when pressed repeatedly about the use of the death penalty against Saddam, repeating his general opposition to capital punishment several times but avoiding direct questions about the former dictator's fate.
"Our position on the death penalty is well known. We're opposed to it," Blair said.
"You oppose his execution?" asked Sky News television reporter Adam Boulton.
"Adam. Excuse me. That is just enough, thank you. ... I happen to want to express myself in my own way, if you don't mind," Blair retorted.
Blair relented under intense questioning, saying in response to other journalists' questions that "We are against the death penalty ... whether it's Saddam or anybody else."