Marseille have been trying to finalise a deal to sign Rennes full-back Rod Fanni on Wednesday.
Skysports.com reported last week that the 29-year-old France international had emerged as a potential target for the French champions after Cesar Azpilicueta suffered cruciate ligament damage.
Fanni had also been linked with English giants Liverpool, but Marseille chairman Jean-Claude Dassier has confirmed they are set to step up their interest.
It is thought the Mediterranean outfit would have to pay about €4million (£3.36m) to sign Fanni, who is under contract with Rennes until June 2012.
And the two clubs seem to have reached an agreement as Marseille are preparing to begin negotiations over personal terms with the former Lens and Nice player.
"There are still a few details to sort out," Dassier told L'Equipe.
"I will call Rennes' chairman on Wednesday and we will be able to start to talk with the player and his agent.
"If the player's demands are too big it will not be sorted out."
Fanni joined Rennes from Nice in 2007 and had been linked with both Everton and West Ham before signing a contract extension in November 2009.