Mohsni has been on trial at West Ham during pre-season as Hammers boss Sam Allardyce casts an eye over the 24-year-old.
The defender, who can also play as a striker, has impressed at Roots Hall over the last couple of seasons.
Mohsni is thought to have caught the eye in pre-season training and West Ham have tabled an offer in the region of £150,000 for the Frenchman.
However, Southend have rejected West Ham's initial offer for Mohsni as they battle to keep hold of the versatile performer.
Mohsni has just a year left on his current deal, after Southend took up the 12-month option they had on him at the end of last season.