Washington: A defiant US President George W Bush unapologetically defended his decision to invade Iraq last year, insisting it had made the United States safer and vowing never to seek permission to wage war in self-defence.

Taking on critics at home and abroad who argue that Bush acted alone and in the face of an unproven threat, the President said he would not shy from conflict even if, after wooing friends and allies to the cause, he lacked broad support.

"From the beginning, America has sought international support for operations in Afghanistan and Iraq and we have gained much support," Bush said in his final "State of the Union" address before he seeks re-election on November 2.

Bush maintained there was no doubt the overthrow of Saddam Hussein had boosted the security of the United States, the Middle East and the world in general.

He ignored criticism that Iraqi weapons of mass destruction (WMDs) - the threat from which formed the basis for the decision to go to war against Iraq - have not materialised despite intensive searches by arms inspectors.

Instead, he pointed to discoveries of facilities and equipment in Iraq that may constitute attempts to develop chemical and biological weapons, mass graves and said the Iraqi people are better off today than they were under Saddam.