United offered De Gea a new contract on reduced terms, which he accepted. But the club have since withdrawn that offer and wanted the 32-year-old to lower his wages even further.
De Gea was the longest-serving member of the United squad before his contract expired. He may well have played his final game for the club after 545 appearances across a 12-year stay.
Onana has had just one season at Inter since arriving on a free transfer from Ajax last summer. He helped the Italian side reach the Champions League final, where they were beaten by Manchester City in Istanbul.
Inter are in line to make a huge profit for the former Cameroon international. United are getting closer to getting their man.