Tapped to lead a Franco-Italian carmaking giant formed by merging Renault SA and Fiat Chrysler Automobiles NV, Jean-Dominique Senard is in Tokyo to make what may be the sales pitch of his career.

In an interview Thursday, he painted a picture of a grand alliance making and selling cars across the globe, keeping people employed and churning out profits.

Convincing the stakeholders of the two auto firms on the merits of a merger may have been the easy part. The hard task is selling the deal to Renault's alliance partner Nissan Motor Co., as well as labor groups and politicians wary of job cuts.