The latest US combat death brought the total to 147, equalling the toll in the 1991 Gulf War, and increased pressure on President Bush, who is under political fire over the spiralling cost of the war and accusations that he misled Americans into the war.

Massachusetts Sen. John Kerry, a Democratic presidential contender, said on Wednesday the Bush administration had "trafficked in untruth" about Iraq trying to acquire uranium, one of the justifications given for the war to oust Saddam Hussein.

Bush said in his State of the Union speech in January that Baghdad sought uranium from Africa to make nuclear weapons. It has since been learned the intelligence reports were partly based on forged documents.

In a closed Senate hearing, lawmakers questioned CIA Director George Tenet about pre-war intelligence on Iraq. Tenet has accepted responsibility for the CIA approving Bush's speech.

In further violence in Iraq, the mayor of a town in a restive region west of Baghdad was shot dead along with his son, a military spokeswoman said.

Central Command chief Gen. John Abizaid said American forces were now engaged in guerrilla war in Iraq and must adapt their tactics to crush an increasingly organised, cell-based resistance spearheaded by Saddam loyalists.

His comments contradicted Defence Secretary Donald Rumsfeld, who said on June 30 that it was not "anything like a guerrilla war or an organised resistance."

Abizaid told a Pentagon briefing the Iraqis "are conducting what I would describe as a classical guerrilla-type campaign against us. It's low-intensity conflict in our doctrinal terms, but it's war however you describe it.

"The level of resistance... is getting more organised and it is learning. It is adapting.... And we've got to adapt to their tactics, techniques and procedures."

The US military had expected a surge of attacks this week to coincide with anniversaries linked to Saddam, the Baath Party and Iraqi nationalism.

Attacks have continued despite a crackdown by American troops in areas north of the capital, once a hotbed of Saddam loyalists.

Abizaid, who replaced the retiring Gen. Tommy Franks as head of Central Command earlier this month, said US troops should be prepared for yearlong deployments in Iraq, a staple of the Vietnam War but used only rarely since then.