While President Reagan, the Air Force and Congress debate the best way to launch the MX missile, $4 million in federal planning money is being spent by Nevada and Utah regardless of whether the MX is ever installed in those states.

The money comes from a Defense Department account called MX Community Planning Funds. So far this year, $2.5 million has gone to Nevada and $1.5 million to Utah. Another $1 million is being held in reserve for planning elsewhere if needed, because one MX scenario puts some missiles in New Mexico and Texas.

"When Nevada and Utah were identified as the preferred alternative for basing the MX, people recognized that they couldn't start planning after the decision was made," said Gary Vest of the Air Force's environmental division at the Pentagon.

The "preferred alternative" for the Air Force is a giant shell game: the continual switching of 200 missiles among 4,600 shelters scattered through the valleys of Utah and Nevada. The theory is the Soviets will never know which shelter is holding a real missile, and thus would be unable to destroy many of them.

Reagan reportedly prefers another alternative -- launching the new intercontinental ballistic missile from airplanes -- but convincing Congress of the wisdom of that choice is going to be difficult.

If the Air Force's alternative goes forward, the impact on nine essentially rural counties in Utah and Nevada would be enormous. Here are the Air Force's estimates, which are disputed as too conservative by Utah and Nevada officials:

More than 75 square miles of land will be needed during the construction phase; more than 39 square miles once the system is operation.

More than 30,000 people will be employed during the peak year of construction; an additional 35,000 will accompany them or work on related jobs. When construction is over, the base will have 13,000 military and civilian employes, many with families. The states' population now totals 2.3 million, most of it in a few urban areas.

At least 20,000 new housing units will be needed during construction.

Schools for construction workers' families will employ 800 new teachers; the finished base will need 375 teachers; about 260 new public employes will be needed for police and fire protection.

Wages and others earnings generated by MX construction will total $1.2 billion in the peak year and will level off at $250 million when the MX is operational.

All this will happen in an area where county governments are almost nonexistent simply because they aren't needed, and nobody ever heard of a community master plan, complete with zoning codes.

"Look at Lincoln County Nev. ," said Lon Wyrick, who is the coordinator for the Nevada MX Local Oversight Committee. "You have 3,700 people in the county. If 4,800 people come in with the MX program , you have more than a 100 percent increase."

Committees of politicians and citizen groups have been set up in both states, staff directors and consultants have been hired and work programs have been drafted and debated. Whether this has been money well spent will not be known until the final decision is made about where MX will be based and how it will be launched.

The uncertainty is straining relations between the Air Force and the two states. "If we had the necessary information, we could plan for it," said Stephen T. Bradhurst, MX project director for Nevada. "If the Air Force would tell us the construction management plan, it would tell us where the people are going to be and how many of them there are going to be."

Chad Johnson, who owns a furniture business in Beaver, Utah, and is chairman of the Beaver County Commission, said that if the decision is put off much longer, "it's going to be a crash project. I think we can handle it, strictly from a planning aspect. But I'm speaking from Utah and we would have two years longer than Nevada."

The preferred alternative starts with MX construction in Nevada, where the main base would be built and located at Coyote Spring Valley. Nevada Gov. Robert List, a foe of MX, is unhappy with the Air Force's draft environmental impact statement for the project.

" . . . We are fiercely proud of our state and our unique quality of life," List said in a recent letter to Air Force Secretary Vern Orr. "The MX missile system represents a threat to that quality of life. It means a loss of solitude, of open space. That part of Nevada would be gone forever."

Officials in Nevada and Utah insist that the planning money is needed while the Pentagon adamantly denies the money is primarily to quiet citizen unrest.

"I don't think the Air Force sees this as buying off Nevada," said Wyrick. "The local policy committee is not for MX or against MX. But if MX is to be deployed, we want to be prepared for it and we want compensation for the loss of life style . . . . We realize that this is a boom and bust thing that has got to be controlled."