The midfielder's move from Sevilla was confirmed yesterday.
Asked about the reasons for his move, he said: "I won some important titles with Sevilla but the Champions League is something you always have in mind, also to enjoy the Premier League and to have a really strong year.
"Truth is this is a dream for me and a challenge to play for a club like Manchester City and fight for titles and everything that comes with that.
"Considering everything, it was the confidence that I could play there and the truth is I am very happy to play for such a big club.
"Individually, above all, City have so many good players and the idea of playing there with such amazing players and fighting for a title - because I feel we have a good team to do that."