The Blues moved nine points clear of City last weekend following their win over Tottenham, but manager Jose Mourinho and John Terry were quick to play-down their tags of title favourites.
City have three games in-hand over Chelsea, and victory in those matches would take them top on goal-difference - but it is the West London outfit who are now regarded as favourites.
However, Cech is sticking to the Chelsea line that City must still be ranked as favourites.
"They are the main title rivals and favourites and now even more when they have three games in hand if they manage to win those games then they will be ahead," Cech told Sky Sports News' Weekend warm-up.
"The advantage with City is that they are out of the FA Cup so they have nothing more to play apart from the Premier League, so they can purely concentrate on that. Whereas we hope to progress to the Champions League and if you play it sometimes can be much harder.
"But the last three years we've been saving English football all the time - everyone got knocked out really early. We might be in the same situation again because let's see how Man United may overcome their deficit but hopefully they will."
Chelsea have performed well against their key rivals throughout the season and Cech feels that has been vital.
"We've been doing really well and we've tried to carry the momentum from Christmas where we did really well," he continued.
"Once you get in the mood and confident and the tranquillity of the momentum. You concentrate on the game and have no distractions and everything seems to keep going."
Cech recently broke Peter Bonetti's club record of clean-sheets, and he admits he is delighted to reach the landmark.
"It's a great joy. It was a great personal achievement, which I never thought before of breaking any records in 2004 when I signed for the club," he said.
"I was happy to be part of a new project of building a new team with a new manager and trying to win the trophies. I always went game by game so you don't really think about records. But as soon as the record was approaching, everybody kept reminding me that I was getting closer and closer and prior to the Hull game I knew it could happen.
"So I was very pleased with that because I've done it not even in ten years. You have to play every time to get a personal achievement like that.
"I am proud that ever since I came to the club I kept my number one spot and kept playing games and that leads to the numbers and obviously number of clean-sheets."