Tony Blair has restated his determination to tackle "repressive states" with weapons of mass destruction.
Tony Blair asked delegates to understand his decision to go to war
The prime minister's comments came ahead of Wednesday's Labour conference debate on the divisive issue of the Iraq war.
Earlier Mr Blair told BBC Radio 4's Today programme that the potential consequences of failing to tackle the threat of states like North Korea getting weapons of mass destruction are "absolutely enormous".
He said that if the US-led coalition had not confronted Saddam Hussein's regime, North Korea would not have been brought back to talks over its nuclear ambitions nor would Iran be co-operating with inspections.
In a reminder of one of Mr Blair's other international interventions, Afghan President Hamid Karzai told Labour's annual conference in Bournemouth how life in his country had improved since the fall of the Taleban.
The Iraq controversy is being discussed on Wednesday afternoon at the conference, where party leaders have been defeated in a vote on foundation hospitals, one of the government's key NHS reforms.
The conference has been extended by half an hour, to 1800 BST, to allow extra time to debate foreign affairs, including Iraq.
In a rare interview for BBC Radio 4's Today programme, Mr Blair said the big security threats facing the world were completely different from those seen during the Cold War.
He said: "It is the prospect of chaos and disorder from a combination of terrorism and these deeply repressive states, states for example like North Korea, spending literally billions of dollars on nuclear weapons capability whilst their people starve...
"I believe if we do not deal with this threat, if it strikes again like 11 September or even worse, I promise you that the consequences for our own safety and security, the stability of our economy will be absolutely enormous."
He vowed to keep up the pressure on North Korea.
He did not know whether the process underway to check on Iran's nuclear ambitions would work, or speculate on what would happen if it did not.
"If we had not taken a stand in respect of Iraq ... how on earth were we going to get North Korea back to a proper dialogue and Iran cooperating with the International Atomic Energy Authority."
He acknowledged he might never persuade critics the war was right but urged them to listen to people in Iraq saying the country was now a better place.
Mr Blair also used the interview to say the most important thing for the government was "to get back out there and have a conversation with the public".
He pointed to the "continual reporting" of evidence at the Hutton inquiry into the death of government scientist Dr David Kelly when most people wanted to know how ministers were addressing their daily dilemmas.
Mr Blair on Tuesday received a standing ovation for his conference speech, in which he vowed to ride out his "rough patch" and said he had "not got a reverse gear".
Afterwards, at the Tribune Rally - the biggest fringe event of the conference - former International Development Secretary Clare Short said if Mr Blair did not change his ways then "we have got to change Blair".
And former Labour leader Michael Foot spoke about "the lies of our leaders" on the issue of weapons of mass destruction.
Delegates are now starting to debate Iraq and will be able to vote on Labour's foreign policy as a whole, after a deal for a 75-minute discussion was reached.
It came after an anti-war emergency resolution from the RMT rail union was thrown out.
The debate is on the section covering the war in the National Policy Report on foreign affairs, which supports the government decision to go to war.
Labour officials insisted that there was always the chance of a debate and a vote on Iraq.
But union leaders said that this deal was only cobbled together on Tuesday night in a meeting of the conference arrangements committee.
On the foundation hospital issue, Dr Reid told delegates Labour was taking health services previous monopolised by those wealthy enough to afford them to make them available to everyone.
But the leadership lost the vote on a Unison union backed motion opposing the plans on a show of hands. The results of a motion backing the government will be announced later.