United, who are on course for a record 20th English League title this season, are runaway leaders with a 15-point advantage over City.
Hart is at loss as to why City have struggled to retain the league this season, but he concedes United's form has had a major bearing in the matter.
"Maybe we have drawn more games than we would have liked to but it has not been a perfect season - and it needs to be pretty perfect to win this league," Hart said.
"We have done well but we have been up against a killing machine that have kept turning out results no matter what.
"It is a tough league. It's hard to win games. Unfortunately when we do lose, United stretch that lead and it has been disappointing but we will keep going.
"We worked so hard to get that title we are never going to just give it away. I'd imagine from the outside it looks that way, but that's just not the case."