LONDON - George W Bush and Tony Blair probably knew they were exaggerating the threat from Iraq when they were making the case for war, according to former chief UN weapons inspector Hans Blix.

The US president and the British prime minister ignored the few caveats in reports from intelligence services on Iraq's nuclear, chemical or biological weapons programmmes, he writes in his account of the months leading up to the US-led invasion.

Blix says it was "probable that the governments were conscious that they were exaggerating the risks they saw in order to get the political support they would not otherwise have had".

Blix was head of the International Atomic Energy Agency from 1981 to 1997 and later chief of UNMOVIC (the UN Monitoring, Verification and Inspection Commission) until 2003.

At other points in his book Disarming Iraq - The search for weapons of mass destruction, due to go on sale on Tuesday, the former Swedish diplomat appears to soften his criticism of the British and American leaders.

"I am not suggesting that Blair and Bush spoke in bad faith, but I am suggesting that it would not have taken much critical thinking on their own part or the part of their close advisers to prevent statements that misled the public," he writes.

"It is understood and accepted that governments must simplify complex international matters in explaining them to the public in democratic states.

"However, they are not vendors of merchandise but leaders of whom some sincerity should be asked when they exercise their responsibility for war and peace in the world."

Blix says he too had believed Iraqi President Saddam Hussein had illegal weapons. He adds, however, he was unwilling to state it as fact until he saw concrete proof -- which was never obtained by his teams of inspectors scouring the Iraqi countryside.

"A number of intelligence services, including the French, were convinced that weapons of mass destruction remained in Iraq, but we had no evidence showing it," Blix wrote.

He quoted French President Jacques Chirac, staunchly opposed to war, as saying intelligence services sometimes "intoxicate each other".

Nearly a year after the invasion and overthrow of Saddam, the coalition has not found illegal weapons in Iraq.

- REUTERS