It has long been speculated that Messi would quit PSG when his two-year deal expired after being suspended by the recently-crowned French champions in early May.
The suspension was for an unauthorised trip to Saudi Arabia.
The 35-year-old has been heavily linked in the media with Saudi club Al-Hilal.
His great rival Cristiano Ronaldo moved to Saudi side Al-Nassr in January.
Former club FC Barcelona, where Messi had spent his entire career before financial problems meant he joined PSG, have also shown interest in his return.
