The two companies need to shed assets generating about 5 billion euros ($6.8 billion) in annual revenue to help persuade competition watchdogs to back the proposed deal, unveiled in April and which would create a combined group with $44 billion in yearly sales.
The companies said they would seek buyers for operations in Austria, Hungary, Romania, Serbia, Britain, Canada, the Philippines, Mauritius and Brazil, a series of sell-offs that would affect some 10,000 workers out of their global total of 130,000 and account for around 3.5 billion euros of sales.
Competition regulators in some 15 countries, as well as the European Commission, are expected to take a hard look at the deal, which brings together the world's top two cement makers with a combined stock market value of more than $55 billion.
Europes top competition regulator, Joaquin Almunia, has said the merger would be subject to an in-depth review, known as a phase 2 examination.
Holcim Chief Executive Bernard Fontana said the companies had already received about 50 expressions of interest from potential buyers and would soon begin negotiations.
He said the assets had been selected based on their geographical and industrial overlap and how swiftly they could be sold at a good price. He did not elaborate. This list represents most of the assets that both companies consider divesting as part of the planned merger. Other divestments will be unveiled in due time, Fontana said.
Lafarge Tarmac employs around 6,000 workers. Lafarges German operations for sale employ some 368 people.