The fate of the missing 350 tons of HMX and RDX explosives, feared to have fallen into the hands of insurgents or terrorists, triggered a second day of claims and counter-claims in the to-close-to call election.

"What did the president have to say about the missing explosives? Not a word. Complete silence," Kerry said, as Bush declined to publicly mention the controversy in campaign appearances.

"George Bush has not offered a single word of explanation, he failed to secure Iraq and keep it from becoming what it is today, a haven for terrorists," Kerry said in a speech in Green Bay, Wisconsin.

Cheney defends silence

Vice President Dick Cheney led the Bush counter-attack at a rally in Pensacola, Florida.

"It is not at all clear that those explosives were even at the weapons facility when our troops arrived in the area of Baghdad. John Kerry doesn't mention that," he said.

"Nor does he mention the 400 000 tons of weapons and explosives that our troops have captured and are destroying," said Cheney, adding that without the US invasion, Saddam Hussein would "be sitting in his palace, instead of jail".

The International Atomic Energy agency said on Monday the explosives, missing from an arms dump south of Baghdad, could be used in conventional weapons or to trigger a nuclear device.

'Attempts to extinguish issue'

Kerry also criticised attempts by White House aides to extinguish the issue, which Democrats say undercuts Bush's central campaign theme that only he can keep America safe from terrorists.

"First they said they couldn't guard the weapons caches because they had other priorities," Kerry said.

"Then they are argued that losing the explosives wasn't really that big a deal, finally at the end of the day, the White House just boldly declared that it just didn't happen," said Kerry.

NBC television meanwhile said in its report on Monday night that US troops "never found" the missing explosives when they arrived at the depot south of Baghdad in April 2003, did not necessarily mean they had already vanished.

"The Bush campaign immediately pointed to our report as conclusive proof that the weapons had been removed before the Americans arrived. That is possible, but that is not what we reported," said anchor Tom Brokaw on his NBC Nightly News broadcast.

Controversy fanned

Kerry's aides meanwhile did their best to fan the controversy, six days before a neck-and-neck election in which both sides are clawing for any perceived advantage.

The campaign unveiled a new advertisement showing the veteran senator in presidential pose, standing in front of a US flag, criticising Bush on the issue.

Bush's "Iraq misjudgements put our soldiers at risk, and make our country less secure", Kerry said in the commercial, to run in markets where Bush will campaign in the closing week of the campaign.

Kerry also lambasted Bush over a Washington Post report on Tuesday that the administration would next year make a new request for funding for the wars in Iraq and Afghanistan.

"We have learned that the president wants an additional $70-billion of your money by early next year for Iraq and Afghanistan, bringing the total cost to $225-billion. Mr President, what else are you being silent about? What else are you keeping from the American people? How much more will the American people have to pay?" said Kerry.