President Bush says he has no doubts about launching the unpopular war in Iraq despite the "high cost in lives and treasure", arguing that retreat now would embolden Iran and provide al-Qaida with money for weapons of mass destruction to attack the United States.

Bush is to mark the fifth anniveresary of the US-led invasion of Iraq on Wednesday with a speech at the Pentagon. Excerpts of his address were released Tuesday night by the White House.

The mother of Samah Hussein cries over his body lying in a Baghdad, Iraq, morgue after he was killed when a suicide attacker detonated a car bomb outside the US military camp Cuervo in Baghdad in this June 13, 2004 file photo. [Agencies]

At least 3,990 members of the US military have died since the beginning of the war in 2003. It has cost taxpayers about $500 billion and estimates of the final tab run far higher. Nobel Prize-winning economist Joseph E. Stiglizt and Harvard University public finance expert Linda Bilmes have estimated the eventual cost at $3 trillion when all the expenses, including long-term care for veterans, are calculated.