New York, Aug. 27 -- A prominent Sikh separatist said Tuesday that the FBI and the Royal Canadian Mounted Police have warned him that he faces a new credible threat to his life even as a man from India faces sentencing later this year for a 2023 death plot against him.

Gurpatwant Singh Pannun, general counsel for Sikhs for Justice, said he was warned by FBI agents who visited him last Thursday that he should not travel until the threat is resolved, and, if he does, the agency should be notified in advance of his plans. He said the Royal Canadian Mounted Police warned him by telephone on Tuesday, though neither law enforcement agency gave any details about the plot that was uncovered. Messages seeking comment from both law enforcement age...