Real Madrid are reportedly preparing a world-record £90m bid for Napoli defender Kalidou Koulibaly.

Koulibaly has been heavily linked with a big-money move to Manchester United in the past two transfer windows, although the Red Devils are so far understood to have been put off by his hefty price tag.

Napoli are refusing to lower their asking price of £90m, which would see Koulibaly become the world's most expensive defender ahead of Virgil van Dijk, who joined Liverpool for £75m last January.

United were still thought to be the frontrunners for his signature, but Italian outlet Il Mattino now claims that Madrid have entered the race and are contemplating meeting Napoli's demands.

Madrid have been tipped to make a number of signings both this month and in the summer, having endured a tumultuous first half of the season.

United remain interested in Koulibaly but were expected to wait until the summer before returning with a bid having made Roma centre-back Kostas Manolas their number one target.