A single Soviet missle, which the Soviets claim was fired accidentally, is closing in on the United States. The president cannot decide whether to respond with a missle or absorb the loss of a million Americans.

This was the scenario shown to an audience of 35 to 40 students last night in Willard Building by retired Army Maj. Gen. Milnor Roberts speaking on the Strategic Defense Initiative and space defense.

Roberts said such a scenario, shown on a program called "One Incoming", is one major reason for further development of SDI.

"The Soviets are accident-prone," he said. "Chernobyl had safeguards."

Charelton Heston, narrator of the program, said the Soviets have been working on an anti-ballistic missle defense system for years and that they have six manned space stations.

"With the space shuttle we can, in five years, put up a non-nuclear defense," Heston said.

Roberts, who is chairman of the lobbying group American Security Council and a member of SDI proponent group High Frontier, said terrorists and "rogue nations" -- such as Libya -- could someday obtain nuclear weapons and use them against the United States.

One of the arguments against SDI is cost. Robert said that a new innovation called "brilliant pebbles" reduces the cost of SDI from $70 billion to $40 billion over 10 years and would eliminate other expensive systems such as the Stealth bomber.

Brilliant pebbles are thousands of small metal particles which would be exploded in the path of a missle, the program said. The kinetic energy built up in space would destroy the missle.

Asked whether the Soviets would simply build more missiles to overwhelm SDI Roberts answered, "If (the Soviets) can't be sure of getting most of the missiles through (they) won't attack." And the Soviet economy is too weak to build enough missiles to counter SDI, he added.

Roberts, who has testified SDI's potential to Congress, said President Bush will probably make a deployment decision on SDI by 1991.

The event was sponsored by the College Republicans.