Telles has a release clause of £36.7million in his current contract at the Portuguese giants.
But Porto are thought to be willing to accept over £10m less in a bid to cash-in while they can - with the 27-year-old out of contract this season, says Correio da Manha.
Telles - who has also attracted interest from Juventus - will therefore be able to negotiate pre-contract terms with European sides from January 1 ahead of a free transfer in July.
Porto are desperate to recoup as much money from the deal as possible.
That is because Telles' former side Galatasaray will be owed ten per cent of any future transfer.
The one-cap Brazil international's agents Pini Zahavi and Jorge Mendes also stand to make 15 per cent of the cut as well.
Telles is thought to have already agreed a five-year deal worth around £70,000-a-week with United.