Vinagre is currently impressing on loan at Wolverhampton Wanderers, where he has made nine appearances in all competitions, and the teenager's performances have reportedly attracted interest from other clubs.
However, the Portuguese Under-19 international has hinted that his long-term future may still lie at the Ligue 1 giants, where the left-back has a contract until 2022.
The 18-year-old told O Jogo: "United is a great club and a dream, like other big clubs in England and Spain.
"At the time, I was very focused on United, because it was a great opportunity, but then the other proposals were studied and I, together with my advisors, thought that the best project for my development would be Monaco."
Wolves are said to be keen on signing Vinagre on a permanent deal either in January or at the end of the season.