* Holcim says interest in assets has doubled in past 2 weeks
* To start discussions with potential bidders in August
* Several parties express interest in buying all assets
* Merger with Lafarge "on track" (Adds details from CEO)
By Caroline Copley and Leila Abboud
ZURICH/PARIS July 21 (Reuters) - Cement makers Holcim and Lafarge have received more than 100 expressions of interest in assets they must sell ahead of their planned merger, the Swiss company's chief executive said on Monday.
The two companies proposed a multi-billion euro series of asset sales two weeks ago in their efforts to get regulatory approval for the planned merger, unveiled in April, which would create a combined group with $44 billion in annual sales.
Holcim Chief Executive Bernard Fontana told journalists at a briefing in Zurich on Monday that the companies had received more than 100 expressions of interest, including from private equity funds and other cement makers, with several parties indicating a desire to buy the entire portfolio of assets.
This is up from the 50 notifications of interest they had received when they published the list of disposals on July 7.
Fontana said the companies would start discussions with potential bidders in August, but declined to say when the deadline for bids would be.
The two cement groups are seeking buyers for operations in Austria, Hungary, Romania, Serbia, Britain, Canada, the Philippines, Mauritius and Brazil to address competition regulators' concerns about their combined market power.
The sell-off will affect some 10,000 workers out of a global total of 130,000 and account for around 3.5 billion euros ($4.7 billion) of sales.
Fontana said "several people" had shown interest in buying all the assets put up for sale, but said the final decision determining the choice of buyer would depend on the price.
European labour unions have asked both cement groups for specific employment guarantees that would be binding for the buyers.
Asked whether Holcim would give preference to any bidders which guaranteed they wouldn't cut jobs or close sites, Fontana declined to be specific but stressed the assets for sale were not restructuring cases.
"It's not an issue. They are good assets. If there was a need (to cut jobs) I would do it," he told journalists at a briefing in Zurich. "The divestments are linked to overlaps. They are good companies, they are competing and this will continue."
He added that the possibility of an initial public offering or spin-off for some of the assets remained an option.
In an interview with the Wall Street Journal published earlier on Monday, Fontana said the merger was "on track" and that the two cement groups were in "advanced" talks with European competition regulators over their proposed combination.
Antitrust reviews are expected in about 15 countries, and Fontana said filings had already been made in the United States, Canada, Mexico, India and Russia, he told the paper.
$1 = 0.7384 Euros Editing by Miral Fahmy and Mark Potter