Pentagon Plans Record-breaking Explosion in Nevada Desert

The Pentagon is preparing to set off a record-breaking bang, detonating 635 tonnes of high explosives and sending a mushroom cloud into the sky over the Nevada desert. The blast, on June 2, codenamed Divine Strake, is likely to be the biggest controlled conventional explosion in military history, experts said, and is designed to test the impact of bunker-busting bombs aimed at underground targets.

The blast comes at a time of rising tension with Iran over its nuclear programme. The US has refused to rule out military action and is considering the feasibility of destroying underground warhead development sites Iran is alleged to have built.

"We have several very large penetrators we're developing," James Tegnelia, head of the Defence Threat Reduction Agency (DTRA) told US defence reporters. "We also have - are you ready for this? - an explosively formed charge that we're going to be putting in a tunnel in Nevada ... and that represents to us the largest single explosive that we could imagine doing conventionally to solve that problem."

The explosive used will be ammonium nitrate soaked in fuel oil - a cheap but potent combination. "I don't want to sound glib here but it is the first time in Nevada that you'll see a mushroom cloud over Las Vegas since we stopped testing nuclear weapons," Mr Tegnelia said.

Ivan Oelrich, a munitions expert at the Federation of American Scientists, said: "I suspect this is primarily a test of their computer modelling abilities, because I don't know how they could deliver a weapon like this. They are looking at how different rocks respond to shockwaves."

The White House and the Pentagon wanted to develop a nuclear bunker-buster bomb, but the initiative was blocked by Congress, obliging the defence department to experiment further with conventional explosives.

Mr Tegnelia's remarks triggered some anxiety in Las Vegas. Shelley Berkley, a Nevada Democrat, told the House of Representatives: "Anytime an administration official starts talking about mushroom clouds and Las Vegas, I want answers."

The DTRA later issued a statement saying: "All explosives, given the right thermal characteristics, create a cloud that may resemble a mushroom cloud."

"The dust cloud ... may reach an altitude of 10,000 feet and is not expected to be visible off the Nevada test site," Major Susan Idziak, a spokeswoman, said. "No adverse impact on the environment or health of exercise participants or local residents is anticipated."