NEW YORK—An alleged al-Qaida operative has missed his first public court date in New York City because of an undisclosed medical condition.

Ibrahim Suleiman Adnan Adam Harun is accused of plotting to kill U.S. diplomats in Nigeria.

The 43-year-old had been scheduled to appear Friday in federal court in Brooklyn. His lawyers showed up without him and told the judge about his condition at a sidebar. The judge agreed not to disclose his ailment.

Prosecutors say Harun killed U.S. soldiers with an al-Qaida force in Afghanistan before joining a plot to bomb a U.S. embassy.

His next court date is May 3.