A former U.S. Army sergeant nicknamed "Rambo," who prosecutors say supervised an international band of hit men and mercenaries, was sentenced to 20 years in prison on Tuesday for conspiring to kill a federal drug agent and an informant.

U.S. District Judge Laura Taylor Swain in Manhattan said Joseph Hunter, 51, deserved a lengthy sentence given the "grave and serious" crimes he committed and his guilty plea to charges including that he conspired to murder a law enforcement officer.

"The crimes you committed are serious, and the sentence you received today reflects that," Swain said.