To reach that stage City must defeat Spanish champions Real Madrid and German champions Borussia Dortmund in their two remaining fixtures to stand any chance.
Even then, other results may see them exit the competition at the group stages for the second successive season. However, Aguero feels that there are still reasons to be optimistic.
"We should never give up," he told the club's official website. "Where there's a will, there's a way, right? Of course, it's harder now because we're not just relying on ourselves but also on the other teams' results.
"What we mustn't do is leave the pitch with any regrets and be content knowing that we have given our all. This club deserves nothing less and our supporters deserve as much, too."
City have picked up two points from four matches so far.