U.S. Marines carried out a successful simulated armored attack against mock Iraqi forces in the Saudi desert Monday but rough seas forced the cancellation of an important sea leg of the Imminent Thunder exercise.

For the second day, military officials canceled the launching of speedy hovercraft vessels, Landing Craft Air Cushions, that are used to quickly ferry supplies ashore to attacking Marines.The hovercraft are an important compenent of any amphibious assault during an "over-the-horizon" attack, a tactic military officials say allows the launching of a speedy attack out of sight from shore.

Officials Sunday postponed the hovercraft landings and cited safety Monday in scrapping that portion of the exercise.

"You know, if it's real world or an operation you execute it," said Marine Maj. Patrick Sivigny, explaining why the Landing Craft Air Cushion vessels were held back a second day and would sit out the rest of the operation.

"But, when it's an exercise - whether it's here, back home in the states, if it's out on sea, shore or land - safety is always a primary consideration and that's what dictates whether or not you postpone any part of an exercise."

While the hovercraft portion of the exercise was scrubbed, Marine commanders from the 3rd Light Armored Infantry were sending eight-wheeled armored reconnaissance vehicles known as LAV-25s into the barren desert to serve as mock Iraqi tanks.

Each of the reconnaissance vehicles represented 10 Iraqi tanks and the purpose was to detect invading scout cars and muster a credible defense against them.

Officials said one of the reconnaissance vehicles did succeed in briefly getting past the range of fire of the mock defenses by accelerating quickly after first traveling at a leisurely pace for several miles.

Despite the one slip, Marine officers were satisfied that had the invading scout cars actually been Iraqi tanks they would have been spotted and destroyed.