The 21-year-old midfielder has emerged as a top target for leading sides across Europe, with Manchester City, Bayern Munich and Tottenham also reported to be keen on acquiring his services.
Ajax have refused to enter into discussions regarding a possible deal, with there no intention on the part of the Dutch giants to part with a prized asset at this stage of his career.
Their resolve has been tested, with Goal revealing that a €30 million (£27m/$35m) bid was tabled by Barcelona over the summer.
The Catalan giants remain keen, with De Jong having hinted a switch to Camp Nou as he pursues his dream of one day playing alongside Lionel Messi.
There is, however, no suggestion as to when a deal may be done, with Ali Dursun unwilling to speculate on what could happen.
Quizzed on the latest reported interest from Madrid and United, and whether those two clubs had approachied him, De Jong’s representative told De Telegraaf: "I can neither confirm nor deny this.
"You should ask Marc Overmars. I send all clubs that contact me over to him."
Former Arsenal and Barcelona star Overmars is currently director of football at Ajax.
He is among those to have stated that De Jong is not for sale, with his current employers under no financial pressure to cash in.
The door is being left open to a future move, though, with the Amsterdam-based outfit aware that they will struggle to retain the services of a player who is now a senior Netherlands international for much longer.