Chelsea boss Antonio Conte refuses to give up on prising Kalidou Koulibaly away from Napoli.
Mirror Football says Chelsea have tabled an improved offer for the defender this week.
Antonio Conte has made Koulibaly his No.1 defensive target and they are now ready to firm up their interest with a mega bid.
Napoli are desperate to keep hold of the Senegal centre half who was also a target for Everton.
The latest bid sees Chelsea raise their offer from €37.5 million to £40 million plus bonuses.
A five-year contract worth €3.75 million-a-season is also in front of Koulibaly and his agent, Bruno Satin.