Victory for City at their Eastlands ground on Monday would see City replace reigning champions United at the top of the table on goal difference with just two games left.
City appeared to have blown their hopes of being crowned champions of England for the first time in 44 years after a 1-0 defeat at Arsenal earlier this month left them eight points behind United.
But they have won three straight league games since that setback while United have faltered in losing to Wigan and being held to a draw by Everton.
Although City manager Roberto Mancini has repeatedly conceded the title to United, Argentina international Zabaleta insisted there was no lack of belief amongst the squad.
"We have to play the same as we play every game," Zabaleta told City's official website. "We need to be strong mentally, focus on what we have to do and give it our all.
"We've got the talent and we've got quality -- we've got everything.
"But behind this the mentality and the attitude for that game has to be more than 100 percent
"I'm sure if we put everything into this game, with the quality we've got it can make the difference."
He added: "We've never stopped believing in ourselves, but to be honest, after the Arsenal defeat I thought our chance had probably gone.
"We've been five points clear before so we know how it feels, but United losing against Wigan and dropping points at home to Everton shows that in football you have to believe, because you just never know.
"If we have another chance for the title it's because we deserve it. We've kept going and we will continue to do that and see what happens.
"We know how important this game is. United are the team we want to beat, especially because it gives us the chance to get back to the top."