The former Middlesbrough and Watford player returns to Italy, where he has previously played for Lazio and Fiorentina.
Australian skipper Okon pulled out of Leeds' reserve team game with Sunderland on Wednesday to fly to Italy to tie up a deal.
His departure will allow Reid to add further to his squad ahead of the 1st September, 5pm transfer deadline.
He revealed today that he is interested in signing another striker, and said to the official Leeds website: "We have a few irons in the fire."
Meanwhile, Reid has confirmed that another Premiership club is looking to take goalkeeper Nigel Martyn.
"Nigel has been a fantastic professional here, and the first thing I said I would do was let him know of any interest," said Reid.
"He turned Chelsea down, which I was very pleased with, but this new offer may be in his interests."