Mundo Deportivo says Dalot was offered up by Erik ten Hag as a bargaining chip for Barca midfielder Frenkie de Jong.
And United believed using Dalot as part of a deal for De Jong would see Barca lower their asking price of £63million.
However, the LaLiga side rejected the exchange as Dalot is not on their radar for the new season. But even if he had been, the deal would have struggled to go through.
That's because Dalot has no intention of leaving Old Trafford.