US District Judge Ursula Ungaro was scheduled to sentence 31-year-old Gufran Mohammed, who faces up to 15 years in prison.
He pleaded guilty in July to conspiring to support the al-Shabaab terror group in Somalia and al-Qaida in Iraq.
Mohammed is a naturalized US citizen from India. He was arrested last year in Saudi Arabia following numerous online contacts with the undercover FBI employee.
Co-defendant Mohamed Hussein Said of Kenya has pleaded not guilty, with trial set in May. He's accused of identifying recruits for a Syrian terrorist group and helping finance al-Shabaab.