The Defense Department plans to spend up to $100,000 for a study entitled "Mikhail Gorbachev -- The Formative Years," based on the recollections of an emigre who hasn't seen the Soviet leader for nearly 30 years.

The idea for the unclassified study came from Gerold Guensberg, head of Delphic Associates Inc. of Falls Church, a self-described "Beltway Bandit" who hires Soviet emigres to write reports that he tries to sell to government agencies.

Several months ago, Guensberg said, he noticed that one of the emigres, Fridrikh Neznansky, had attended the Moscow Law Institute from 1950 to 1954, the same years as Gorbachev, and worked in the same city after graduation.

"Did they know each other? Yes. Were they close friends? No," said Guensberg, who said he retired from the Central Intelligence Agency in 1979 after years as an interrogator of German scientists who had been in the Soviet Union.

Guensberg said he then approached the Pentagon, contemplating that the study could be finished before next month's Geneva summit between Gorbachev and President Reagan. At the same time, he realized that Neznansky's material is dated and might not be entirely accurate.

"He knew Gorbachev. I also know there was a danger. He doesn't have a license to practice psychiatry," Guensberg said.

The study is for the Defense Department's "net assessment" office, which is responsible for calculating the balance of forces between the Soviet Union and the United States.

Guensberg said he went to the net assessment office -- rather than the State Department or the CIA -- because he knew Andrew Marshall, its director, and knew that Marshall's office had money.

Marshall couldn't be reached for comment yesterday, but Lt. Col. Thomas Gladstone, his military assistant, said the office wants to fund the study in hope of learning "some insights about this man Gorbachev , what makes this guy tick, how he might react."

Gladstone wouldn't say how much the study might cost. "It's a fairly small amount," he said. "Just say it's less than $100,000."

The Pentagon announced its intention to negotiate with Guensberg's company on a sole-source basis in the Oct. 11 Commerce Business Daily, which lists many government contracts.

The announcement said the study "will focus on what may have been unique about Gorbachev that led to his eventual rise to the highest party level. This research will provide defense policy makers with insights . . . which could directly impact on U.S. national policy concerns toward the Soviet Union."

Guensberg said Marshall "deserves a medal for realizing the potential in this," but added that he was disappointed it has taken so long to award the contract.

Guensberg declined to say how much of the proposed contract award he will share with Neznansky, who left the Soviet Union in 1978 and now resides in Germany where he works for an emigre publishing house.

But he added: "This isn't something waste-conscious Sen. William Proxmire D-Wis. would get excited about. It's not a study of why birds flap their right wing. This is serious. They need every scrap they can collect."

Guensberg said Neznansky last saw Gorbachev in the mid-1950s when the two were working near Stavropol, Neznansky as a prosecutor and Gorbachev as an official in the Young Communist League.

To help Neznansky recall those days, Guensberg said he gathered Soviet scholars from George Washington, Harvard, Columbia and Stanford universities and had them debrief Neznansky during a series of meetings in September.

"In my opinion it has merit," Guensberg said, adding: "Obviously I have a vested interest."