PARIS—Four days after Fiat Chrysler Automobiles NV proposed a merger to France’s Renault SA, a French government official phoned the Italian-American company to say France wouldn’t be forced into any deal.

Bruno Le Maire, France’s finance minister, was irritated to read in a French newspaper that Fiat Chrysler considered its proposal “non-negotiable.” The minister, who was attending the exclusive Bilderberg meeting of global business and political leaders, spoke with Fiat Chrysler chairman John Elkann and said that to the...