United remain favourites to land the Bulgarian - but only if they meet Spurs' £30million asking price.
So far, United have not budged from £25m and, if they do not up their bid, Spurs will listen to Barca.
And they would be far more willing to reach a compromise deal with them, than negotiate with United.
A White Hart Lane insider confirmed: "Barcelona are watching the situation very closely and we know they would love to sign Dimi."