The Stamford Bridge club currently sit third in the Premier League, two points adrift of leaders Arsenal, while United languish in seventh.
Yet Mourinho insists winning the title is not his top priority as he keeps one eye on Chelsea's future.
|11/4||Chelsea are 11/4 with Bet365 to win the title this season|
"We are not desperate to win the title. I keep saying the same," he said. "We want to build a team for the future, find a transition between the Chelsea of the last decade and Chelsea of the next decade.
"But we will try to fight for the title until the end."
The Portuguese feels his players will need to be wary of David Moyes' men and stressed they would be foolish to underestimate a team of United's pedigree.
"We don't play against a team that is 11 points behind the leader; we play against the champions, we play against Manchester United," he continued.
"Many times on many occasions the team that looks to be in the most difficult situation is the team that appears stronger in that match.
"That's why I consider this game especially dangerous for us."
Mourinho, who is gunning for his 100th Premier League victory, would also like to see his opponents field a full-strength side on Sunday.
"I would prefer [Wayne] Rooney and [Robin] van Persie [who have each been sidelined with injuries] to play," he remarked.
"I prefer to play against the best players. I think the concentration is bigger when they are there."
Chelsea confirmed the re-signing of midfielder Nemanja Matic from Benfica on Wednesday, and Mourinho has backed the Serb to make a big impression at Stamford Bridge, while revealing he will not start against United.
"I'm sure he will [make a big impression]," he added. "I'm happy he has come now because it gives him time to adapt before next season.
"His profile as a player is, for me, the perfect one."
"[But] I feel that I hold that respect to my players. I don't think it is the right message for them that a new player comes and immediately plays in the team."