The Portuguese said that he is "calmly waiting for news" regarding the move, whilst confirming that Henrikh Mkhitaryan, who is expected to move in the other direction, will not be considered for selection against Burnley.
"Not selected. But in very good condition, training really well," Mourinho said of Mkhitaryan.
When asked about the move for Sanchez, Mourinho said: "There is no point in trying to hide or deny, but it is not done at all.
"So in this moment, Mkhitaryan is our player, Sanchez is an Arsenal player and with a match tomorrow I want to switch off and focus on the most important thing, which is the match.
"I think clearly everybody knows that we are there and especially when Arsenal manager speaks so clearly like he did."
Sanchez's contract is due to expire in just six months' time and United have reportedly agreed personal terms with the Chilean, with the i's and t's of the deal just needing to be dotted and crossed.
Mourinho went on to say that he has not been personally involved in the negotiations and was simply waiting to hear how discussions are going, much like anyone else.
"Sometimes people thinks transfers involve a lot the managers in the negotiations," he explained. "I think it depends on the profile of the club, the way we establish our jobs. In my case, when it goes to the table of negotiations, I like to be out. I am out and I will just calmly waiting for news, no more than that.
"I will speak with you if one day we sign him, I can speak with you about him and what he can bring to our team. He's an Arsenal player, he's not my player, there's no point in me speaking about something that may or may to happen.
"My involvement in the situation is just to say the reasons why I would like to have the player and no more than that, I'm out. Let's be clearer if it happens. If it doesn't happen, there is no point.’ "
With the transfer now dragging on, Mourinho was aksed why, to which he replied: "I don't know."
Sanchez will not be able to feature against Burnley, even if he completes his move late on Friday, after missing the registration deadline.