The 25-year-old Frenchman, who joined Wolves from Saint-Etienne in August 2012, was part of the team that got relegated from the Championship last season.
"I was told I could speak to Fulham and now I don't understand the delay," Sky Sports News quotes Sako as saying.
"I would like things to be sorted out. I am only being ambitious. I believe the fans will understand that.
"In the difficult moments we had last season, they were very good to me and I hope they saw someone who gave everything back to them."
Sako has two years left on his contract at Molineux.