The Reagan administration has decided to deport Ndabaningi Sithole, a former African revolutionary who sought political asylum in the United States so that he would be free to promote private enterprise as the cure for Africa's political troubles, Sithole said yesterday.

Sithole, the leader of one of the major black nationalist factions that fought white minority rule in what is now Zimbabwe, said that his request to remain in the United States was rejected, although he will be allowed to appeal the decision.

In an interview, Sithole said if he were forced to return to Zimbabwe, "it would be like returning to imprisonment or returning to the grave."

Sithole, the founder of the political movement now run by Prime Minister Robert Mugabe, fled Zimbabwe in 1984 after surviving several assassination attempts that he contends were mounted by the government. He has been living in the United States since 1985.

In exile, he produced one unabashedly pro-American book and is working on another. In both works, he holds that African independence has been a disappointment largely because of disastrous Marxist economic policies adopted in much of the continent.

In a recent interview, Sithole said that his ideas frequently paralleled the U.S. government's Africa policy.

Under the circumstances, he said, he had expected the administration to applaud his efforts to promote open societies and free-market economies in Africa, "but I was mistaken in my assessment."

A State Department representative said the department has a policy against commenting on specific asylum cases.

Sithole, who lives in Silver Spring, said he was told that conditions in Zimbabwe do not warrant grants of asylum because opposition political leaders such as Joshua Nkomo are living freely in the country. Sithole scoffed at this rationale, noting that attempts have been made on Nkomo's life.

Sithole, 68, is a Congregationalist minister, but in the years that preceded Zimbabwe's independence in 1980, he was best known as a political leader. He was sentenced to six years at hard labor in 1969 for "incitement to murder" Prime Minister Ian Smith of what was then white-ruled Rhodesia.

Sithole founded the Zimbabwe African National Union but lost control of it to Mugabe during the seven-year guerrilla war against the Smith regime. His faction failed to win representation in Zimbabwe's first parliamentary election, which Mugabe won in February 1980.