The new deal will keep the 20-year-old at the club until 2014.
“Last week, we extended his deal by five years,” he explained on Calciomercato.it.
“The previous expiry date was set for 2012 and it is now June 2014. Of course, we also adjusted his wages, but out of respect for the lad and the club, we prefer not to reveal the terms of the agreement.”
Sanchez has been a reported target of Premier League champions Manchester United.