He now wants to start a professional career in Europe and has joined up with the United squad at Thorp Arch.
The centre-back, who is 6ft 4in, holds an American passport, but has been involved in several of Nigeria's international squads.
American striker Mike Grella signed an 18-month contract at Elland Road in February after scoring a hat-trick while on trial in his first match for Leeds' reserves.
Grella, a USA U-20 international, turned down an offer from MLS side Toronto FC in order to launch his football career at Leeds and has since made six substitute appearances for the first team.