United chased De Jong all summer and had agreed a free with Barcelona, but the Dutchman rejected the chance to move to Erik ten Hag's side and was determined to stay in Spain - despite the Catalan club being keen to sell him.
United's interest in De Jong was a long-running saga in the summer transfer window, with the Red Devils chasing the 25-year-old before eventually giving up and signing Casemiro from Real Madrid.
De Jong rejected the chance to move to United several times and regularly cited his desire to remain at Barcelona.
It has been widely reported that the Catalan side owe him millions after he took a wage cut to help the club during a time of financial crisis, a fee he would miss out on if he were to leave Barca.
Ten Hag is not put off by the midfielder's resistance to leave the Spanish giants and the United boss believes he can persuade his former Ajax colleague to join him in England.