Nine-year-old Terence Karamba left New York Sunday night to return to his native Zimbabwe, two months after allegations that his father, a diplomat, abused him, touching off an international incident.

The youth was accompanied by a Zimbabwean social worker and assured that he would not be returned to the custody of his father, U.S. authorities said.

"We reached the stage in his therapy where he was ready to go," said Robert J. McMahon, executive director of the private social services agency that has cared for Karamba since mid-December.

McMahon said he was told by Zimbabwean and U.S. officials that the boy will be placed in foster care, under the aegis of the courts and the Zimbabwean Ministry of Social Welfare, and that the Karamba family will receive counseling toward the goal of an eventual reunion.

"With any of these cases, there's always a lump at the bottom of your stomach," he said, "but I think the level of risk is as low as you can possibly get it."

Karamba became the subject of an international conflict after public school authorities in Queens told New York City authorities of the suspected abuse by his father, an administrative attache to Zimbabwe's U.N. mission.

A city agency investigated and charged that Floyd Karamba had savagely beaten Terence. A court petition alleged that the father more than once had stripped his son, "tied his arms behind his back with wire or rope, his legs together and hung him by his bound arms from a pipe in the basement . . . then beaten Terence with an electrical extension cord."

Terence was removed from his parents' home and assigned to St. Christopher-Ottilie Services for Children and Families, which placed him in foster care. Criminal charges against Karamba were dropped because of his diplomatic immunity, and he was expelled from the United States. His wife eventually joined him.

When the State Department sought custody of Terence to return him, the boy refused to leave his foster home.

Zimbabwean officials threatened retaliation if Terence was not returned, and the case quickly moved through the court system as Legal Aid attorneys sought political asylum for the boy. Six weeks ago, the Supreme Court cleared the way for his return.

From the beginning, officials at St. Christopher-Ottilie agreed that he should return eventually but sought time for psychiatric treatment. He needed to overcome his immediate fear of return and place his trust in an adult who could accompany him home, they said.

McMahon said Sen. Daniel Patrick Moynihan (D-N.Y.) interceded to persuade the State Department that Terence should not be returned immediately. The department agreed to wait until psychiatrists, including its own consultants, said he was ready.

"We received what we asked for, which was time to work with the boy," said Gary Kipling, a St. Christopher-Ottilie official who served for a time as Terence's foster father. "And, given the time, he went back to Zimbabwe.

"He wasn't kicking, he wasn't screaming. He went under his own steam, and the most important thing is he was able to say, 'I'm ready.' He reestablished that he could trust an adult, and he was able to transfer that to" the social worker, he said.

Sources at the State Department and in New York City said Floyd Karamba is believed to be in counseling under the auspices of the Ministry of Social Welfare and the United Methodist Church.

The State Department, which sent a psychiatric consultant to accompany Terence home, also has engaged a law firm in Harare, Zimbabwe, to monitor the case.