The Italian said fifth-placed Newcastle would approach the game against Premier League leaders City in an extremely confident mood after their 2-0 victory at Champions League finalists Chelsea on Wednesday.
"Newcastle played a fantastic game at Chelsea and I think this game will be more difficult for us," Mancini told reporters on Friday.
"The Manchester United game was at home and we played very well to win 1-0 but Newcastle is away and I think it will be harder."
"Cisse is incredible," said the Italian. "He scored two fantastic goals against Chelsea.
"He has 13 goals in 12 league games for Newcastle and he's a good player. But not just him, their whole team is playing very well.
"They play to win in every game, they have a good mentality and for this reason I think it will be a good game on Sunday."
"Our players know they have everything in their own hands," he said.
