Tuesday, May 9, 2006; Posted: 10:10 p.m. EDT (02:10 GMT)

LAS VEGAS, Nevada (AP) -- A non-nuclear explosion expected to generate a mushroom cloud over the Nevada desert will be postponed while a federal court reviews plans for the blast, officials said Tuesday.

The experiment won't be conducted earlier than June 23, said Cheri Abdelnour, spokeswoman for the federal Defense Threat Reduction Agency at Fort Belvoir, Virginia. The blast was originally scheduled June 2.

In April, the Winnemucca Indian Colony and several Nevada and Utah "downwinders" filed a federal lawsuit seeking to block the blast. The suit accuses the government of skipping public comment and failing to complete required environmental studies before picking a date and place.

In documents filed Monday, Justice Department lawyers sought to push back until early June a hearing in the case. The judge did not issue an immediate ruling.

The lawsuit claims the planned 700-ton ammonium nitrate and fuel oil bomb will kick up radioactive fallout left from nuclear weapons tests conducted from 1951 to 1992 at the Nevada Test Site.

The suit also claims the blast will irreparably harm land that members of the Western Shoshone tribe have never acknowledged turning over to the U.S.

The blast, some 85 miles northwest of Las Vegas, is expected to generate a 10,000-foot mushroom cloud and a shock wave that officials say will probably be felt 35 miles away.

The Defense Threat Reduction Agency claims the explosion will help design a weapon to penetrate hardened and deeply buried targets. Critics have called it a surrogate for a low-yield nuclear "bunker-buster" bomb.