Sam D. Starobin, director of the D.C. Department of General Services for a decade, became the seventh agency head to leave office as a target of Mayor Marion Barry's campaign to remove allegedly incompetent or undesired top aides from city government, according to reliable sources.

Starobin, who was the last military appointee under the old three-commissioner form of District of Columbia government, told the mayor yesterday he would leave office within the next three months to accept a job at an undisclosed location outside the city, the sources said.

During Barry's campaign for mayor, Starobin was one of those placed on a 'hit list' of department heads to be removed if and when Barry became chief executive of the city.

A source close to Starobin said yesterday that the DGS director felt no direct pressure to leave the post, even though Barry had removed six others before him.

"It's obviously a new team and the director just thinks he won't be a part of it," the source said. "He has no animosity. He has no rancor. Starobin's seen enough of politics not to take this personally."

Florence Tate, Barry's press secretary, refused either to confirm or deny Starobin's eminent departure.

"The mayor has nothing to say about any reported resignation," she said. "He will announce any resignation in a timely fashion."

While some in city government considered Starobin one of the more open administrators surrounding former Mayor Walter E. Washington, others accused him of having an ironhanded grip on the city's leasing and procurement operations.

A former military man, Starobin was privately accused of favoring past military associates, being independent of the mayor and by-passing blacks in the awarding of city leases and contracts.

A major aim of the Barry administration is to increase the number of contracts awarded to minority-owned businesses, beyond the legally required 25 percnet -- which has never been reached -- to perhaps 50 percent or more, according to Barry administration officials.

Starobin's pending departure is considered the opening of doors to enhance that effort and also a poltical plus for Barry, who in some circles of the black community was being childed because five of the first six agency heads to leave under his administration were black.

"Marion had been finding all of these allegedly incompetent black folks," one Barry adviser said yesterday. "Folks were beginning to wonder when he was going to find somebody white who was incompetent, too."

Only one of the previous six agency heads removed by Barry -- former planning director Ben W. Gilbert -- was white. The other five were black: housing director Lorenzo W. Jacobs Jr., acting labor director Thomas A. Wilkins, city administrator Julian R. Dugas, licenses director James W. Hill and human rights director James W. Baldwin.

There was no indication yesterday when Barry would formally announce the reported resignation of Starobin or when a replacement might be chosen.