Paolo Di Canio's side are set to complete a move for the 18-year-old full-back, who has been previously linked with a switch to Arsenal
The 18-year-old, who has been previously linked with a move to Arsenal, is a left-sided defender and would cover the departure of Danny Rose, who has returned to Tottenham following a season-long loan spell at the Stadium of Light.
Louvel has also revealed Olympique Lyonnais were in the running with Paolo Di Canio's side to sign Mendy.
"We have agreed with Sunderland for the transfer of Mendy," Louvel told RMC.
"It is now up to him to agree with them. We're ok."
"OL? We were close to an agreement with Lyon. It did not happen, but you never know..."