Speaking after his side's 1-1 Barclays Premier League draw at Sunderland, Van Gaal remained coy over the rumours.
He told Sky Sports: "I think always the club has to announce it. And when we think it's the right time to form a transfer then we will come to you and say we have bought that player or the other player.
"But at this time we can't say anything."
The Dutchman added: "Yes (I like Di Maria) but I like Messi also. There are a lot of players in this world that I like but they can't always come to Manchester United."
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