On Sunday afternoon a week ago, Bruno Lafont, the chief executive of Lafarge took a call from Wolfgang Reitzle, the chairman of Swiss cement company Holcim, seeking to merge with its French rival. He had bad news.

Holcim Ltd and Lafarge SA reached an agreement to adjust merger terms in an effort to salvage their bid to form the world’s biggest cement maker, leaving open the contentious point of who will be chief executive.