Banned from the squad that drew with Chelsea on Saturday after refusing to substitute against Tottenham last week, the 37-year-old has had difficult talks with Erik ten Hag.
Limited to just two Premier League starts this season, the Portugal captain is still keen to leave the club, having failed to make a move away over the summer.
Finding a buyer, however, could prove difficult. Approaching 40 and on a huge salary, it has been reported that no offers at Champions League level are forthcoming.
United’s Premier League rivals Chelsea have considered the former Real Madrid and Juventus star but put interest aside before signing Raheem Sterling and Pierre-Emerick Aubameyang.
United host Sheriff Tiraspol in the Europa League on Thursday night and Ronaldo could feature for the first time since his public breach of discipline.