Man Utd boss Jose Mourinho had tabled a £80m bid for Napoli defender Kalidou Koulibaly.
United boss Jose Mourinho has made no secret of his desire to sign a centre-back but was left empty-handed last summer.
Italian newspaper La Republicca claim United now have launched a €90 million [£80m] bid for Koulibaly to solve their defensive woes.
It is said United’s initial bid, which eclipses the world record defender fee of £75m that Liverpool paid for Virgil van Dijk in January, has been rejected.
Napoli president Aurelio De Laurentiis is reportedly asking for upwards of €100m [£89m] for the 27-year-old.