The move comes after a swap deal involving Leeds United's Michael Duberry was rejected by the City Board.
Leeds had offered to pay £14,000 out of Duberry's £24,000 a week wages for the rest of his contract but the cash conscious City Board voted against paying out the £4,000 a week to cover the former Stoke defenders wages.
John has took his time to settle in at Highfield Road since joining in September and has twice been booed by the City supporters for poor performances.