Switzerland-based Holcim Ltd. has rejected the terms of a proposed $44.27 billion merger with France's Lafarge SA.

The decision was announced March 16 and it appears the two big sticking points are over the stockholder share exchange ratio, as well as who will lead the combined operation. The deal reportedly calls for Lafarge Chief Executive Bruno Lafont to take the helm. According to a statement from Holcim:

... the Holcim Board of Directors has concluded that the combination agreement can no longer be pursued in its present form, and has proposed to enter into negotiations in good faith around the exchange ratio and governance issues.

LaFarge said in a separate statement that it's only willing to revisit the terms of the exchange rate.

Lafarge's Board of Directors remains committed to the project that it intends to see implemented. The Board said it is willing to explore the possibility of a revision of the parity, in line with recent market conditions, but it will not accept any other modification of the terms of the existing agreements.

The news has made headlines in media outlets including The Wall Street Journal, Associated Press and Bloomberg. 

Per The Wall Street Journal, it appears that some key Holcim shareholders began privately rejecting the terms last week, spurred by the fact that since the deal was first announced last April, Holcim's stock has outperformed Lafarge. At that time, the plan was called a "merger of equals" by both companies. Now that the overall merger is in limbo, it raises questions about several smaller deals on both sides, set in motion to clear antitrust regulations.

The Wall Street Journal notes:

The new questions surrounding the deal follow months of effort by Holcim and Lafarge to shed businesses and operations where they had significant overlap, part of a complicated process of winning antitrust approval in countries and jurisdictions around the world. Last month, Holcim and Lafarge said they had negotiated a more than $7 billion deal to sell Ireland’s CRH PLC cement factories and other facilities in Europe, Canada, Brazil and the Philippines.