He told the media earlier this week: ""There is the possibility of playing for Valencia, who are a great club, but right now I want to be fully focused on the Argentina national team and on the World Cup." It seems as the player isn't too keen on moving right now and would rather wait after the world cup is over, which makes sense as he wants to be calm and relaxed when playing in the world cup.
The management at the club wants to finish the deal before the world cup though as they believe his price could increase after the world cup and the important thing would be an agreement between the two clubs.