United tabled a £26million offer for the former Arsenal skipper yesterday and Fabregas, 26, would relish the switch.
A Spanish source said: "Cesc would only go if Barcelona agreed to sell him.
"The Barca midfield is already looking very crowded for next season and you wonder how many games Cesc will start.
"He wants to play in the World Cup next summer and needs to be playing regularly.
"Arsenal have first refusal on him but he'd prefer a switch to United."