The 22-year-old has become one of the most sought-after prospects in football after a superb season in Serie A where he hit 11 goals in 34 appearances.
President Maurizio Zamparini confirmed negotiations were at an advanced stage but refused to comment until after the sale was completed.
Now, vice-president Giglielmo Micciche has confirmed that Chelsea and PSG are leading the race for the player's signature but is unsure as to where the player will be plying his trade next year.
“Chelsea or PSG? Both London and Paris are two beautiful cities, and both represent a great opportunity for Pastore,” Micciche told Calcio Mercato.
“At the moment there are negotiations in progress and it is a situation which is involving the president Zamparini, along with the boy's attorneys.
“We're talking about a major player and therefore important figures. We're looking for the best solution for both parties.
“I'm sure, however, that Pastore will join the team that shows the most desire to secure his signature.”
A fee of around £35.1 million was the reported asking price for the player but it remains to be seen what the exact figure will be.
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