Manchester United are prepared to wait until the summer to sign Kalidou Koulibaly with hope diminishing that the defender will be allowed to leave Napoli in January, sources have told ESPN FC.

The Senegal centre-back is on United's list of options as they look to bolster their defence along with Inter's Milan Skriniar, AC Milan's Alessio Romagnoli and Leicester's Harry Maguire.

United had hoped Napoli's exit from the Champions League would increase their chances of landing the 27-year-old this month.

However, the Serie A side have so far refused to negotiate and United now believe a deal in the summer is more likely.

Sources have told ESPN FC that Koulibaly, who signed a new contract in September that could keep him at Napoli until 2023, is open to a move to Old Trafford.

Caretaker manager Ole Gunnar Solskjaer has been told by executive vice-chairman Ed Woodward he will get a say on any January additions but the Norwegian has made it clear he is happy to work with the players already at his disposal.