The Portuguese striker is now on the brink of sealing his switch to Glasgow, but the two clubs are still holding talks.
Celtic hope to finalise an agreement with his club Vitoria Guimaraes on Friday, with a fee of around £2million expected to be agreed.
Balde has attracted interest from a number of clubs after netting nine goal in 27 appearances last season, but Celtic are poised to finalise the deal.
The African-born forward arrived in Glasgow earlier this week, and the 22-year-old is poised to become Neil Lennon's latest signing.
Lennon admitted the club had been keeping a close eye on the player and was confident he would add more physical presence to his strike force.
"He is a player we have scouted and looks the type we would like but whether we can get a deal done or not, I don't know," Lennon told STV last week.
"We are just looking to strengthen that area. Balde is a big striker and has the physical attributes we are looking for. But he is interesting other clubs."