Wolff, Mercedes' motor sport boss, admitted that the German marque looked for a new partner following news McLaren is switching to Honda power for 2015.
"It's clear that we are losing an engine customer in 2015 and for Mercedes it is important to have a regular business case so it is important to have at least three customers from 2015 onwards," he said in Monaco.
"That is why we are having certain discussions with teams and Williams is one of them.
"It would be for 2014."
But while Renault is losing Williams, the French marque is expected to keep Lotus and Caterham on the books for 2014, in addition to Red Bull and Toro Rosso.
The latter deal could be announced in Monaco on Sunday by Renault president Carlos Ghosn, Auto Plus correspondent Jean-Louis Moncet reported.