The trio have been named in England's 33-man Elite Player Squad for the forthcoming tournament but there are fears they may be unavailable for training sessions in the build up to the competition.
Rob Andrew, England's director of elite rugby, has admitted that discussions with Stade and Toulon are ongoing but insisted that he hopes there will not be a repeat of last year's public argument which erupted when Stade's president Max Guazzini claimed England were holding his side to hostage regarding the release of Haskell.
"We are having dialogue at the moment," former Lions Test star Andrew told PA Sport.
"It is inevitable that they will (put the pressure on). They have all got big games.
"Inevitably there are going to be issues that we are working through. How they play out we will have to wait and see.
"We have been absolutely consistent from day one with all these guys and the French clubs about what the situation is and it hasn't changed."
Martin Johnson takes his England squad to Portugal in the last week of January as part of his final preparations for the tournament opener against Wales on February 4.
With the Top 14 season continuing that week, there could yet be problems to be resolved if Wilkinson, Palmer and Haskell are not to become involved in a tug of war between club and country.
"The French league play on the Thursday night that we are in Portugal," added Andrew.
"We expect them in Portugal and we expect them to be there when Martin Johnson wants them there.
"If Martin decides they can play at any stage that is a decision Martin takes for the benefit of the individual player and the England team. That is the top and bottom of it."