Almost nothing about this desolate area just south of the Iraqi border, suggests it as perhaps the biggest and most expensive defense construction project on earth -- King Khalid Military City.

At a projected cost of $9 billion, the task of building the military city in this remote corner of Arabia is beginning to rival Cam Ranh Bay in South Vietnam as a feat of engineering. There are no soldiers, but 7,000 laborers are at work, part of a $1.2 billion consortium laying the city's foundation.

The vast project is part of Saudi Arabia's multi-billion-dollar national effort to bolster its security while upgrading the military training facilities for its uniformed officers.

The major focus of this concern is the network of oil fields traversing the Eastern Province of Saudi Arabia along the Persian Gulf. Although about 27 percent of the world's petroleum is buried underneath those sands, it is almost totally exposed to military attack.

As the Saudis are the first to acknowledge, Arabia is virtually unprotected by anyone -- at least formally. With at the most 7 million inhabitants. Riyadh must defend a nation with one-third the territory of the United States, almost 1,600 miles of coastline and a thousand miles of ill-defined and sensitive borders.

Arrayed against potential external threats are no more than 95,000 Saudis under arms compared to 493,000 in Iraq, the most powerful Arab neighbor. Saudi Arabia could put 170 jets in the air against the 370 of Iraq. Saudi Arabia's 1,000 or so tanks would confront more than 1,500 in any conflict with Baghdad.

Saudi defense strategy seems based on blunting attacks for several days until help -- most likely U.S. help -- arrives. King Khalid Military City is a cornerstone in this plan, although until recently it was only a highway for Bedouin tribesmen and their herds at nearby Wadi Al Batin.

Planned as a center for 70,000 people in the 1980s, the scene is dominated by the din of trucks, bulldozers and jackhammers -- the advance party of American and Third World workers camped literally in the middle of nowhere.

A frequent comparison of the jobs magnitude is with Cam Ranh Bay, the giant Vietnamese facility constructed during the U.S. military buildup in Southeast Asia in the 1970s. A combine of Fischbach & Moore of Texas and Morrison-Knudsen of Idaho -- both heavily involved at Cam Ranh -- has joined with a Dutch firm for preparatory work on the military city here.

At peak strength, 18,000 workers, mostly Asians and Africans, will be camped here. An entire port 200 miles away at Ras Mishab is being laid in to handle the tons of materials and equipment that are needed. Just to keep track of the operation, the consortium has installed a $26 million computer -- dust free -- in a region with some of Arabia's worst sandstorms.

As the team preparing the military city for permanent development later on, it is the combine's task to construct life-support systems for such a harsh environment. They are putting down roads and power generators. An intricate water system with wells as deep as 5,000 feet, has to be completed, as well as communications and radio networks.

More than $550 million already has been consumed and not a single permanent structure is yet up.

"But 18 months ago all that you saw here was sand," one worker says.

At the military city, there is even a temporary pavilion for King Khalid, built at a cost of $3 million for formal dedication ceremonies. But the monarch spent less than an hour there.

A giant, five-bay pre-cast concrete plant is going up at the military city. The forms it produces will be used to actually build the military cantonment and to form the core of the industrial center later on. About 25,000 servicemen, three bridges, are scheduled to arrive in the 1980s for air training and permanent duty.

Some purely military work is underway, although the Saudis are very sensitive about this. Outside the perimeter, for example, South Korean contractors are erecting the first of several of the military city's missile batteries. Although Riyadh has not acknowledged such activity, a visitor can see the facility's structures going up on the low hills in the distance.

Despite such activity, Saudi Arabia appears to find just as much military value in merely populating this area.

The fewer than 3,000 Saudis in this village comprise the major urban area for hundreds of miles. At peak strength, about two-thirds of the military city will be support personnel and families.