Pastore revealed on Tuesday afternoon that only a successful medical stood between him and a move to France.
Chelsea had been interested in the Argentina international, but PSG are reported to have paid ?37million to get the deal done.
Pastore's confirmed move to PSG could therefore precipitate a third Chelsea bid for Modric, after the club revealed at the weekend that they would weigh up whether to make another offer for the Croatian this week.
"You can officially say that I will be a Paris St Germain player, although I still need to do the medical and review some details," Pastore wrote on his official website.
"I want to be a part of Paris St Germain, which is a great club with a great history."
Arsenal boss Arsene Wenger has been moved to describe PSG as the "Manchester City of France" after they lured AC Milan boss Leonardo to take over as sporting director before reeling off a host of new signings to challenge for the Ligue 1 title.
Pastore, who spent the past two seasons at Palermo, is arguably the most significant so far and he the 22-year-old admitted he had been swayed by the ambition of the club.
"Marcelo (Simonian, his agent) and I were talking about this. I care very much about the sporting project, that is why. I talk about it a lot," he added.
"I am very eager to begin this new phase. They explained the project and immediately seduced me to the challenge."
Pastore, who has won nine Argentina caps, has immediately set his sights on winning trophies with PSG and believes they can bring the league title back to the capital for the first time since 1994.
"Winning the local tournament and the cup - I want the team to succeed in everything," he added.
"In particular I will give my best in every game. It makes me immensely happy that they trusted me."
Source: Team Talk
Source: Team Talk