Kerry pounced on reports by the International Atomic Energy Agency that the explosives that could be used in conventional or nuclear bombs had disappeared, as proof Bush had failed as US commander in chief.
"George W. Bush, who talks tough, talks tough, and brags about making America safer has once again failed to deliver," Kerry said.
"After being warned about the danger of major stockpiles of explosives in Iraq this president failed to guard those stockpiles.
"Terrorists could use this material to kill our troops, our people, blow up airplanes and level buildings," Kerry said.
"Now we know our country and our troops are less safe because this president failed to do the basics, this is one of the great blunders of Iraq one of the great blunders of this administration.
"The incredible incompetence of this president and this administration has put our troops at risk and our country at greater risk than we ought to be."
"The unbelievable blindness, stubbornness, arrogance of this administration to do the basics has now allowed this President to once again fail the test of being Commander in Chief.
Nearly 400 tons of powerful explosives that could be used in conventional or nuclear missiles disappeared from an unguarded military installation in Iraq, the IAEA said Monday.
The Iraqi ministry of science and technology informed the IAEA of the disappearance of nearly 380 tons of mainly HMX and RDX explosive materiel on October 10, agency spokeswoman Melissa Fleming told AFP, confirming a report in The New York Times.
"It can be used in a nuclear explosion device, for the explosion," she said, adding: "That's why it was under IAEA verification and monitoring" before the March 2003 US-led invasion of Iraq.
The New York Times said the materiel "could produce bombs strong enough to shatter airplanes or tear apart buildings."