The possibility that the Soviet Union "has achieved a breakthrough" in directing an energy beam to destroy missiles "is considered remote," the Pentagon said yesterday.

Thomas B. Ross, assistant secretary of defense for public affairs, issued that statement&in response to an Aviation Week & Space Technology magazine story which said the Soviets are far along in developing a beam of charged particles to destroy missile and "are preparing to test" an antisatellite laser in space.

"U.S. officials are coming to a conclusion that a decisive turn in the balance of strategic power is in the making," the magazine said in its May 2 issue , "which could tip that balance heavily in the Soviets' favor through charged-particle beam development and the development of energetic strategic laser weapon."

The magazine did not name any U.S. officials who had come to that conclusion. Editor Robert Hotz, in an introductory editorial, said that recently retired Air Force intelligence chief Maj. Gen. George J. Keegan Jr. had helped verify Soviet advances in "a directed-energy beam weapon."

Keegan has been sounding the alarm in numerous public appearances since leaving the Air Force about the Soviet military threat, including beam technology. Aviation Week & Space Technology said the Central Intelligence Agency had rejected Keegan's conclusion, presented while in office, that Soviet "beam weapons development is evident."

Ross, after checking yesterday with Defense Secretary Harold Brown, said in his statement:

"Senior officials of the Department of Defense do not believe that the Soviet Union has achieved a breakthrough in research which could soon provide a directed energy beam weapon capable of neutralizing ballistic missile weapons. Based on all information now available to the U.S. intelligence community, this possibility is considered remote."