Federal prosecutors asked a judge Wednesday to imprison a Turkish banker for over 15 years for helping Iran evade economic sanctions, saying he was a key player in undermining efforts to curb Iran’s nuclear ambitions.

The U.S. government said in papers filed in Manhattan federal court that Mehmet Hakan Atilla lied at a trial that ended in January as he tried to minimize his role in a multiyear scheme to launder billions of dollars in Iranian oil proceeds.