The French international has been heavily linked with a move to the Magpies this summer, and the two sides have now reportedly agreed a fee.
Courbis told RMC Sport: "This is not done yet. Talks continue about the traditional bonuses. I'm not really worried about the outcome.
"Laurent and Louis [Nicollin] were right to say no to a first offer which was upsetting. We're getting close. It's done at 90% but not at 100% yet."
The midfielder scored 14 goals in 37 appearances last season.