City announced on Thursday the manager has put pen to paper on an agreement that will keep him at the Etihad Stadium until the end of the 2022-2023 season.
Since taking the job in 2016, Guardiola has led the club to two Premier League titles, three Carabao Cup triumphs and FA Cup glory on one occasion.
However, he feels there is still more to be achieved, with City having failed to get past the quarter-finals of the Champions League during his tenure.
"In the end we decided that the best for all of us is to continue because still we have the feeling that there is still unfinished business and still there is something to do and continue what we have done in the last years," Guardiola said.
"This club won in the recent past, but together we won a lot and we won a lot and we won again.
"The target at this club, like in the past has not won a lot of titles, is to continue to try to maintain the structure of the club as long and as much as possible.
"That's why I still have the desire to help with all the fantastic players we have for the next years, especially for the fans and we will feel proud of the way we play and the way we win."
Guardiola's new deal means he is set to be in charge at City for longer than the four years he spent at the helm of Barcelona, and he credited chairman Khaldoon Mubarak with convincing him to remain at the Etihad Stadium.
Of Mubarak, he said: "Well, I'm not living daily with him. I am, of course, closer with all the players, the backroom staff and Txiki [Begiristain, sporting director] and Ferran [Soriano, CEO]. But I would say this time the reason why I extended the contract is for our chairman.
"He convinced me we still have to move forward, to continue what we have done in these incredible last four years together and try to do it knowing how tough it will be in the Premier League and Europe, and [with] the desire to, if it's possible, make a step forward in this club or maintain the level we achieved in the last seasons."