Rooney's future has been the subject of intense speculation since former United boss Sir Alex Ferguson revealed that the striker had submitted a transfer request at the end of last season.
"It is a tricky question because, from the ethical point of view, I cannot speak of players of other teams," Mourinho told reporters.
"But you know me, it is not my kind of character to speak with hypocrisy and I speak what I think and he is a player I like very much.
"I cannot say much more that than, but being fast and direct, I like him very much, but he is a Manchester United player."
Rooney was today sent home from United's pre-season tour of Asia due to a hamstring injury.