Guardiola's team will win the Premier League crown if Arsenal lose to Nottingham Forest, or City beat Chelsea the following day - but the former Spain international insists it won't be easy to get over the line.
Speaking before the latest round of Premier League fixtures, he told the BBC: "Tennis players say to serve to win Wimbledon is the most difficult one.
"It's non-stop. Of course we are satisfied to play the Champions League final but now is coming the most difficult thing.
"But on Sunday the game is in our hands to win the most important competition."
City have been on an exceptional run of form since the last international break, while Arsenal - their title rivals - have struggled in recent weeks.
Despite this, Guardiola insists it's not necessarily a reflection of City's mentality.
Reflecting on the Premier League title race and City's recent form, he explained: "Now we talk about mentalities because we won. And I don't believe in that. I defend the team when we lose and they had the same mentality.
"This is the reality. To recover eight points on Arsenal - first we had one game in hand in that moment, so it was a little bit fake but we knew we had to win almost all games and they had to drop it.
"If Arsenal had maintained the same rhythm as the first leg [half of the season] and doing what they had done it would not be possible to catch them. But they drop a few points and we were there. Again, another season, and that means a lot to us."