THUNDERDOME BASE, Saudi Arabia (AP) _ In preparation for the ground battle to come, the desert skies are filled with Apache attack helicopters that could play a key role in battling Iraq's tanks.

A passenger skimming low in a Blackhawk helicopter at more than 100 mph sees columns of M1-A1 tanks rehearsing for combat while Apaches swarm in a ''high-energy assault'' against an imagined Iraqi enemy.

In the misty distance, more bug-like choppers stand in clusters on the sand.

Below, vacated encampments seem ghost towns in the desert, neatly outlined by massive earthen berms.

While not yet joined in battle, the Army is on the move. Its main units are ''jumping'' northward to new base camps every few days, and its combat forces are clearly spoiling for a fight.

''We're awaiting our opportunity,'' said Lt. Col. Bill Hatch, 40, of El Paso, Texas, commander of an Apache helicopter battalion in the 1st Armored Division.

''Wars aren't usually won until you get a guy down there standing on the ground saying, 'We own this place.'''

A report by the General Accounting Office last autumn criticized the Apache, saying its battle readiness was low and maintenance requirements high.

But in Saudi Arabia commanders insist the aircraft has been reliable, and they expect the Army's top-of-the-line attack helicopter to do its job.

The AH-64 Apaches are equipped with laser-guided Hellfire missiles and are designed principally for supporting a ground assault by killing tanks.

On a training operation Saturday, the helicopter battalion streaked low across the sands from staging point to staging point, paused one last time to regroup, then charged en masse at the imagined enemy, an oncoming rush of Iraqi T-72 tanks.

In one of the first battalion-sized rehearsals the unit has conducted since its arrival, the helicopters trained in daylight - albeit on a dismal and blustery winter day.

But in battle, commanders said, the helicopters would prefer to attack at night. The Apaches have night sights and sophisticated radar systems and are able to hit targets at distances of five miles or more.

They are expected to be crucial in keeping down U.S. casualties on the ground.

''When we strike, it's going to be swift and complete to minimize casualties,'' said Col. Johnnie Hitt, 45, of Wills Point, Texas, commander of the 1st Armored's 11th Aviation Brigade.

Hitt said that so far, Iraqi tanks generally ''have moved from one prepared position to another'' where they are able to dig in and survive aerial attacks. ''They had a good plan, and they've executed that plan,'' he said.

But the U.S. response is designed to flush the tanks into the open, making them vulnerable to helicopters.

''Once his tanks are on the move, Apaches are virtually unstoppable,'' said Reid Fail, 30, of Scappoose, Ore., one of the senior warrant officers expected to participate in the tank battles.

''The mobility and deep-strike capability of the Apaches will be the most critical link to victory on the ground,'' said Lt. Col. Terry Branham, who won a Silver Star for flying choppers in Vietnam and now commands the squadron of Apaches likely to make the first run at Iraqi armor.

Iraq's fleet of more than 130 attack helicopters is ''almost as maneuverable as ours,'' said Branham, and those choppers ''were not a priority during the initial air strikes.''

As a result, nearly one-third of the pilots in the squadron will be assigned to engaging Iraqi helicopters in air-to-air combat.