Manchester United are locked in talks with Porto for the signing of left-back Alex Telles.
The Brazilian is out of contract next summer and the Portuguese club want to sell to raise funds.
United are close to getting a deal done for the 27-year-old, having agreed personal terms
But according to Correio de Manha, Porto have raised their transfer demands due to several pre-agree clauses.
They owe Galatasaray a sell-on clause of 10 per cent as well as fees to super agents Jorge Mendes and Pini Zahavi.
To cover the costs, the Portuguese have raised their asking price from €20m (£18m) to €27m (£24.7m).
Telles will reportedly sign a five year deal and earn £3.6 million per year if he signs with United.