The 24-year-old joined City from Valencia in a £25million deal earlier this summer.
“I wanted my future sorted out before the World Cup and Manchester City showed serious intent,” he said.
“They made it very clear they wanted me and were happy to stick their necks out. I wanted to pay that back.”
He added: “I have come here to win titles and important trophies. This club is going to places I want to visit.
“I can’t wait to play alongside Carlos Tevez, Emmanuel Adebayor, Nigel de Jong and Yaya Toure, and that’s to name just four.”