Dubbed "the merchant of death," he lived openly in Moscow, where he reputedly had ties to the Russian intelligence services, until he was lured to Thailand by US agents posing as members of the FARC looking to buy weapons.
US District Court Judge Shira Scheindlin delayed the hearing, originally scheduled for March 12, following a request by the defense, according to court officials.
Bout, 45, was convicted in November in New York federal court, concluding a marathon operation by US authorities to incarcerate the larger-than-life figure popularly dubbed "the merchant of death," in a case that infuriated Russia.
He faces at least 25 years behind bars for conspiring to sell weapons to Colombia's FARC, a US-designated terrorist organization that prosecutors said Bout believed to be plotting to kill US service members.
The mustachioed Russian is widely believed to have been the world's biggest black market arms dealer in the post-Cold War period, specializing in arming African warlords and dictators. He says he worked exclusively as a private air transporter -- although sometimes carrying legal shipments of arms.
Scheindlin ruled in favor of a February appeal by Bout's lawyers to let him out of solitary confinement for the first time in 15 months.