Even without Saddam Hussein, the "new" Iraq still has the technical know-how to resurrect its nuclear bomb programme if it feels threatened by neighbours, Blix says.
The former chief UN arms inspector, who helped oversee the dismantling of Iraqi weapons programmes, sets out proposals for a less "nuclearised" world in a 27-page epilogue to a new, paperback edition of his book Disarming Iraq, first published a year ago.
In the intervening year, more evidence has accumulated to debunk US claims that Iraq had operational nuclear, chemical and biological weapons programmes - President George Bush's stated reason for invading two years ago.
American arms hunters now acknowledge the weapons did not exist.
Blix's criticism of US leaders and their British allies, sometimes muted in the past, grows sharper in this updated book, published by Bloomsbury of London.
Their "exaggeration and spin" and "shrill" claims "helped to mislead the world into believing there were stocks of weapons of mass destruction in Iraq ready for use", the Swedish former diplomat writes of the Bush White House and British Prime Minister Tony Blair.
The chief US weapons hunter, Charles Duelfer, now concedes that Hussein's government had not built such arms since 1991, when UN inspectors, including experts of the Blix-led International Atomic Energy Agency, began destroying weapons stocks and equipment after the first Gulf war.
"[Their] exaggeration and spin and shrill [claims] helped to mislead the world into believing there were stocks of weapons of mass destruction in Iraq ready for use"
In his report last October, Duelfer contended, without presenting hard evidence, that Hussein in 2003 "intended" to rebuild the weapons in the future.
But Blix notes that Iraq would have remained under intrusive, open-ended UN monitoring for years to come, controls that the Bush administration repeatedly ignored in raising alarms over a supposed Iraqi threat.
Know-how still exists
Now, with the UN inspectors driven out by the US-British invasion, Iraq still has "the theoretical and technical know-how" to revive advanced weapons programmes, Blix writes, including the expertise built up by hundreds of Iraqi nuclear scientists and engineers in the atom-bomb project that was derailed by the 1991 war.
Add to this neighbouring Iran's status as a "near nuclear weapon state" - one whose secretive programme is the subject of international negotiation - and the situation "should trigger a more active discussion of the idea of a zone free of weapons of mass destruction in the Middle East, including Israel and Iran", Blix writes.
Although Israel will neither confirm nor deny it, experts think it has 75 to 200 nuclear weapons.
Blix notes that the 1991 UN Security Council resolution authorising the UN disarmament of Iraq envisioned a negotiated prohibition on WMD in the Middle East.