Sevilla confirmed on Monday night they had accepted an offer from City for the 27-year-old Spain winger, with reports suggesting the deal could be worth up to £24million.
Speaking on Tuesday, Navas was quoted as saying by the Spanish media: "We've been talking with Manchester City for four months. The decision is taken.
"There had been rumours (about Real Madrid), but Manchester City were in from the start and I had decided some time ago. It's a good project and it was the moment to make the step.
"The Premier League is a competition where the football is very fast. I'm really looking forward to it. Manchester City are making a great team.
"I'm going from Sevilla, which is a very nice place, and I'm going to a great club in England."
He added on Sevilla's official website: "It was my choice. I'm very happy with the decision. I wanted to continue growing there and they've put a lot of faith in me and I want to continue doing well there.
"It's difficult because I've spent many years enjoying playing in front of these fans but I've made my decision, I wanted to go there. It's a good step for me and I never had any hesitation.
"I want to thank the (Sevilla) fans and the club for all that they've given me."