The Whites have shaken off their disappointment over failing to land Cody Gakpo from PSV Eindhoven and are pushing to bring in a striker.
Dieng has emerged as the top target for the club over the course of the day and they have been making rapid progress in talks to sign him.
It has been claimed that Marseille have already accepted the bid from Leeds for the 22-year-old striker.
Leeds tabled an offer worth over £10m and Marseille were happy to give their consent.
With a deal in place between the two clubs, Leeds are now looking to work out an agreement over personal terms with the striker.
Dieng is yet to give his approval to Leeds and is considering other options on his table as well on deadline day.
Leeds are hopeful that they will be able to convince the forward to move to Elland Road today.
The Whites will arrange for a medical for the player once they work out a deal with his representatives.
