Wolves Player of the Year Sako is set to seal a £4million-plus move to Fulham next week, as Wolves were hoping to complete Wolves head coach Kenny Jackett's first signing in Crewe midfielder Luke Murphy.
With Wolves resigned to Sako's departure, the player's representatives have negotiated with the Craven Cottage club and an agreement on personal terms is in place once the fee is thrashed out.
But Wolves chief executive Jez Moxey and his close friend, Fulham counterpart Alistair Mackintosh, are still haggling.
Moxey, aware Sako is easily Wolves' most expensive asset, is keen to drive the price as high as possible, just like he did successfully last year with Steven Fletcher and Matt Jarvis.
Fulham remain leading contenders for Sako's signature but Lille, Lyon and Marseille are keen to take the winger back to France.
Sako wants to prove himself in England and there are one or two other clubs in this country who could come to the table if the move to west London falls through.
The departure of Sako would be the third winger Wolves have lost this summer, with Stephen Hunt freed and Adam Hammill sold to Huddersfield.
And Jackett has already put out feelers for a natural replacement on the left.
He said: "Sako is the only natural wide left player in the squad and, if he does go, that would need some attention. And we would need that option in the squad? Yes.
Sako pleaded with the club to make his Premier League dream a reality.
The winger is waiting for the chance to agree terms with Fulham while the clubs haggle over a fee.
Wolves want £4m-plus for the 25-year-old, who joined them last August from St Etienne.
Sako says the club promised him he would be allowed to leave if Wolves weren't promoted last season.
The former France Under-21 international has also been told he has a chance of making his country's 2014 World Cup squad - and playing in the top flight would give him a platform to stake his claim.
"I came to Wolves to help them back to the Premier League," said Sako. "When I came here, the club told me if we didn't get promoted to the Premier League, they would find a solution. I want my future sorted out as soon as possible. Then Wolves can move on and strengthen their squad and I can achieve my dream."
Sako reported back for pre-season training this week and insists he will remain professional.
"I will always respect Wolves," he said.