A powerful Trident 2 missile veered off course Tuesday and exploded seconds after launch from a submarine off the coast of Florida - a major failure for the first sea launch of the Navy's deadliest nuclear weapon.

A frequent target of anti-military protesters, the three-stage $26.5 million missile, carrying a load of dummy warheads, was fired from the USS Tennessee at 11:20 a.m. EST while the giant submarine was cruising submerged east of Cape Canaveral.Propelled from one of the Tennessee's 24 missile tubes by a powerful charge of compressed gas, the first stage of the 126,000-pound solid-fuel missile ignited as planned seconds after the rocket cleared the ocean surface.

"A Navy Trident 2 D5 performance evaluation missile was launched from the submerged submarine USS Tennessee, the first Trident submarine configured to carry the Trident 2 missile, at 11:20 EST today (Tuesday) off the coast of Florida," said an Air Force spokesman.

The spokesman said the "exact cause of the malfunction can't be determined until telemetry data is studied."