Last updated on .From the section Chelsea
A four-year deal is in the works for the Senegalese defender, who is expected to join the Blues.
The player is going to Los Angeles on Wednesday to have a medical.
Nathan Ake is close to joining the Blues.
The gap left in central defence was bridged by the pair.
On Wednesday, it was confirmed that the signing of England forward Raheem Sterling from Manchester City was worth £50 million.
Since joining the Italian top-flight side, Koulibaly has made over 300 appearances for the club.
The University of California, Los Angeles (UCLA), and the University of California, Berkeley are training for the tour match against Club America.
The men will play Charlotte FC in Charlotte on Wednesday, 20 July, before taking on the club in a game in Florida.