He told The Sun: “I cannot wait to play in the same team as Cristiano Ronaldo, who is a great player, as well as Wayne Rooney and many more.
“I could not imagine I would ever get to work with a manager like Sir Alex Ferguson but it has happened.
“What can I say? It is a dream the size of the world.”
The former Gremio and Porto star has revealed United is the club he has always wanted to play for.
He continued: “Gremio was my first club and then I moved to Porto.
“Both teams have a great place in my heart, for which I have the biggest affection.
“They were very important in my life and professional growth.
“But ever since I was a boy, I always wanted to play for Manchester United and now that dream has come true. I am very happy.”