"Some 380 tons of explosives powerful enough to detonate nuclear warheads are missing from a former Iraqi military facility that was supposed to be under American control, the U.N.'s nuclear watchdog says.

Melissa Fleming, spokeswoman for the International Atomic Energy Agency (IAEA), told CNN the interim Iraqi government reported several days ago that the explosives were missing from the Al Qaqaa complex, south of Baghdad.

The explosives -- considered powerful enough to demolish buildings or detonate nuclear warheads -- were under IAEA control until the U.S.-led invasion of Iraq in March 2003. IAEA workers left the country before the fighting began."

"U.S. weapons experts say their immediate concern is that the explosives could be used in major bombing attacks against U.S. or Iraqi forces. The explosives, mainly HMX and RDX, could be used to produce bombs strong enough to shatter airplanes or tear apart buildings. The bomb that brought down Pan Am Flight 103 over Lockerbie, Scotland, in 1988 used less than a pound of the material of the type stolen from Al Qaqaa."

"Q But after Iraqi Freedom, there were those caches all around, wasn't the multinational force -- who was responsible for keeping track --

MR. McCLELLAN: At the end of Operation Iraqi Freedom there were a number of priorities. It was a priority to make sure that the oil fields were secure, so that there wasn't massive destruction of the oil fields, which we thought would occur. It was a priority to get the reconstruction office up and running. It was a priority to secure the various ministries, so that we could get those ministries working on their priorities, whether it was -

Q So it was the multinational force's responsibility --

MR. McCLELLAN: There were a number of -- well, the coalition forces, there were a number of priorities at the end of Operation Iraqi Freedom."

"Insurgents issued a warning on Tuesday, saying any U.S.-led offensive in Falluja would lead to attacks on Iraqi and coalition troops with "weapons and military tactics they have not experienced before."

On an APTN video monitored by CNN, a masked gunman read a statement promising a counterpunch against U.S., Iraqi and multinational targets throughout Iraq "in the ways and forms of our choosing."