United have resolved to meet Dalot's buyout clause of €20 million (£17.5m/$23m), and a source close to the operation says the Red Devils are hoping to have the deal done before the week is out.
A naturally right-footed player, Dalot has shown his versatility by also playing on the left side throughout his Porto career.
Dalot has represented Portugal from under-15 to under-21 level and made his Porto debut in October.
Seems like a poor guy can't write scout reports for a few hours without his mentions and DMs being exploded into an insane mess of Diogo Dalot questions.More news: Washington Capitals' Tom Wilson defends hit on Vegas Golden Knights' Jonathan Marchessault
The Telegraph write: "United are also in the market for another full-back, a left-back, to strengthen in that area also".
It is expected that United will make around five signings this summer, with a raft of players, probably including Marouane Fellaini, leaving as Mourinho revamps his squad.
Matteo Darmian is expected to join Juventus in a £10 million deal this summer and there are still doubts about Luke Shaw's long-term future.
The Spain worldwide has two years left on his deal with the Catalan club and talks over a new deal seem to have stalled.
However, the Portuguese is now closing on a move to Manchester United and according to Portuguese daily O Jogo, his representatives have communicated his decision to Porto.