British Prime Minister Gordon Brown has told the Iraq inquiry the 2003 war was "right".
He insisted he had not been kept in the dark by his predecessor Tony Blair in the run up to the invasion.
Mr Brown said he had been convinced by his own intelligence briefings that Iraq was a threat that had to be dealt with.
But the main issue for him was that Iraq was in breach of United Nations resolutions and that "rogue states" could not be allowed to flout international law.
If the international community could not act together over Iraq, Mr Brown said, he feared the "new world order we were trying to create would be put at risk".
The BBC reports Mr Brown began the session by paying tribute to the "sacrifice" made by British servicemen and women, but added: "I think it was the right decision and made for the right reasons."
Setting out his thinking on the rationale for war for the first time in public, Mr Brown said terrorists and "rogue states" were the "two risks to the post-Cold War world" and had to be tackled.
He said he had met the intelligence service five times during 2002 and early 2003 and was given information "which led me to believe that Iraq was a threat that had to be dealt with by the actions of the international community."
Mr Blair gave evidence to the inquiry in January. He said he had "no regrets" about removing Saddam Hussein from power and insisted the Iraq war had made the world a safer place.
The inquiry is examining events from 2001 to 2009, including the decision to go to war, whether troops were properly prepared, the conflict and what planning there was for its aftermath.