Washington: Hillary Clinton charged on Monday the Iraq war may end up costing Americans $1 trillion (Dh3.6 trillion) and further strain the economy, as she made her case for a prompt US troop pullout from a war "we cannot win".

This week marks the fifth anniversary of the US invasion of Iraq, but voters now say the economy is their top issue in the campaign for the November presidential election.

Clinton, the former first lady who is trying to convince voters she has foreign policy gravitas, criticised both her rival for the Democratic presidential nomination, Illinois Senator Barack Obama, and the Republicans' choice, Arizona Senator John McCain.

She said the war has sapped US military and economic strength, damaged US national security, taken the lives of nearly 4,000 Americans and left thousands wounded.

"Our economic security is at stake," she said. "Taking into consideration the long-term costs of replacing equipment and providing medical care for troops and survivors' benefits for their families, the war in Iraq could ultimately cost well over $1 trillion. It has already cost $500 billion."

Swipe at Obama

Clinton said that while Obama insists he will withdraw US troops in Iraq within 16 months of taking office, his former foreign policy adviser, Samantha Power, had said he might not follow through on the pledge.

"In uncertain times, we cannot afford uncertain leadership," Clinton said.

Obama, who routinely scolds Clinton for having voted for a 2002 Senate resolution that authorised the war, fired back.

Quick to retort

"I think Senator Clinton has a lot of chutzpah, as they say, to in some way to suggest that I'm the person who has not been clear about my positions on Iraq. I have been opposed to this war from the start," he told PBS.

Meanwhile, in a potential blow to Clinton's campaign, Florida's Democratic Party said it would not hold a rerun of the state's invalid primary election, leaving a decision on what to do with the state's delegates entirely to the national party.