The striker is set to join the Premier League side after a fee and personal terms were agreed, but Jean-Michel Aulas expects the deal to take another week to be completed
Aulas revealed on Friday that the two clubs have agreed a fee of around €10.3 million for the 28-year-old, who scored 16 goals in 37 Ligue 1 appearances last season.
Gomis has since settled on personal terms, but Aulas feels it will be just over a week until he becomes a Newcastle player, although he has not given a reason for the delay apart from hinting at "minor issues".
"With one year left on his contract he has to be sold because an extension was not an option for us or him," Aulas told L'Equipe. "I did not mean to cause any harm to Gomis on a personal level. I merely needed to sell him.
"We have accepted Newcastle's conditions and Gomis has accepted theirs too. It could still go haywire. There are minor issues which could cause problems. Either way, the deal won't be done for another eight days probably."