The White House announced yesterday that Robert D. Blackwill, the National Security Council's top expert on European and Soviet affairs, will return to Harvard University's Kennedy School of Government this fall.

Blackwill has a history of moving between academia and government, serving as an associate dean and faculty member of the Kennedy school from 1983 to 1985, before being named chief negotiator at Vienna talks on Mutual and Balanced Force Reductions. In 1987, he rejoined the Kennedy school for two years, leaving at the start of the Bush administration to join the NSC. A career diplomat since 1967, Blackwill had held posts in the State Department and at embassies around the world.

Another top NSC staff member, Condoleezza Rice, senior director for Soviet affairs, is also considering returning to academia, officials said. Rice, the only black and only woman in a senior foreign policy position at the White House, is on leave from Stanford University.

Another of what Harvard calls its "scholar practitioners," Roger P. Porter, has not indicated any intention of leaving his post as domestic policy adviser to the president. Porter, like Blackwill, has gone back and forth from the Kennedy school to Washington but has told associates he plans to stay put here for a while.