Some are worried that the merger of Havas with Vivendi might compromise the ad-buying of the agency. Both parties have sought to allay such fears.

Havas noted a current agreement keeps its media buying unit separate from the Vivendi unit. Vivendi said Havas will continue to bid against other ad companies for access to distribution space and content productionl

The entertainment multinational, which owns properties primarily in the music, TV, film, video game and telecommunications industries, has submitted an offer to purchase an approx. 60 percent stake in the global advertising and communications services group from French holding company Bolloré Group for a reported €2.36 billion (about $2.56 billion).

That investment group, which is Havas’ main single shareholder, is led by billionaire investor Vincent Bolloré, who is also Vivendi’s largest shareholder. Vincent’s son Yannick Bolloré is Havas' CEO. Yannick Bollore, in a statement to employees, said he was coming to the deal first and foremost as chief executive.

Groupe Bollere said it has “welcomed” the deal and that it has “decided to enter into discussions with Vivendi."

Yannick during a November interview in Barcelona told Reuters that such a merger could “make sense,” and posited that it's the sort of deal that “would be a development project rather than a cost saving project.”

Yannick also sits on the Vivendi board.

Vivendi owns French TV operator Canal+ Group, Rome-based telecommunications company Telecom Italia, French video game developer Gameloft and video platform Dailymotion, as well as Universal Music Group, which owns record labels such as A&M Records, Capitol Records, Def Jam Recordings and Virgin Records.

Paris-based Havas, which staffs about 18,000, owns PR agencies such as Havas PR and New York-based Havas Formula, as well as financial communications powerhouse Abernathy MacGregor Group and London-based healthcare PR agency Just:Health Communications.