In the complex world of defense contractors, Graham Allison is a special breed.

As dean of the John F. Kennedy School of Government at Harvard University, Allison helped his prestigious institute land a $1.6 million contract two years ago to teach management skills to senior Defense Department officials.

As a veteran foreign policy consultant, Allison landed himself a job last month as special adviser to Defense Secretary Caspar W. Weinberger.

The part-time job will pay Allison $260 a day to be "an intellectual strategic reserve, infusing new ideas and concepts on the substantive side of defense," according to a Pentagon statement announcing his appointment.

Weinberger welcomed him as "a valuable addition" to his personal staff, and the statement said Allison's assignment will "require and include access to all parts of the Department of Defense."

Allison has told Harvard faculty members that his Pentagon work will not interfere with his academic post. But the two roles could collide when the Kennedy school's contract with the Pentagon expires Sept. 30. Then, Allison could find himself advising the defense secretary while his institute negotiates a new agreement.

The Pentagon is now considering whether to extend its arrangement with the Kennedy school, and it is unclear whether Allison would play a role in the negotiations if it does.

A month before his appointment, however, he wrote Weinberger suggesting that the program be extended and expanded. The May 13 letter, which he addressed to "Dear Cap," said the school's three courses for Pentagon officials were "among the most ambitious executive development programs we have undertaken with any government department and one of the most exciting programs for the school . . . . I think this will prove to be of enduring value to the country."

Academic observers who question whether Allison's dual role poses a potential conflict of interest say that while he derives no financial gain from the school's contract with the Pentagon, he gains institutional credit for Harvard.

"What if he was an official of General Motors while serving as an adviser to Weinberger, and General Motors was getting contracts?" asked one source in academia.

Allison, who became dean in 1977, has consulted in the past for the Pentagon as well as the State Department, Central Intelligence Agency and Office of Management and Budget.

He could not be reached for comment.