Koulibaly, 27, is said to be open on the idea of leaving Italy after the recent racism incident in a Serie A fixture against Internazionale.
According to reports in Italy, the French-born defender notified the club he would like to open contract talks with United.
This after The Red Devils interest was previously confirmed by Napoli president Aurelio De Laurentiis - which would've ranked as the world-record transfer for a defender.
— Koulibaly Kalidou (@kkoulibaly26) January 8, 2019
"[Jose] Mourinho wanted him, we rejected £95million," De Laurentiis said in December, as per Calcio Mercato. "But now [after Mourinho's sacking] it's impossible that he leaves Napoli."
However, that has not appeared to deter United and reports on Tuesday claimed the club had renewed attempts to land the centre-half and were indeed ready to test Napoli’s resolve to keep a player who only signed a new five-year deal at the club in September.
English publication Metro stated Koulibaly has been notified that his current £80,000 a week wages would be doubled if he were to arrive at Old Trafford.
However, De Laurentiis is adamant he won’t be sold this month and wants the player to form the cornerstone of their bid to win the Europa League – a competition he believes the club can win.