Wary of the heavy investments needed for the deployment of the new mobile technology, Arcep's president Sébastien Soriano said earlier this week that the minimum price for the sale of the spectrum should not be higher than 1.5 billion euros.

France's economy ministry has the final word on the floor price for sale.

"The floor (price) that we're proposing seems reasonable to us," Junior Economy Minister Agnès Pannier-Runacher told French newspaper Les Echos. "It's up to the government to assume its responsibilities and decide."

Arcep kicked off the long-awaited sale of 5G spectrum on Thursday, ending months of intense debate between the country's four telecoms operators and authorities on how to best deploy the new mobile technology.

Disagreements between the finance ministry and the telecoms authority over the spectrum to be auctioned and the minimum price for the 5G frequency blocs postponed the process, two sources close to the matter told Reuters this week.

For French authorities, the key issue is to find the right balance between raising cash from the sale and avoiding putting an excessive financial burden on telecoms operators so that the deploy the pricy technology fast.

Germany and Italy have raised about 6.5 billion euros each through 5G spectrum auctions, an amount that shocked the industry and raised concerns among the four French telecoms operators -- Orange, Altice Europe's SFR, Iliad and Bouygues -- whose margins are already suffering from a protracted price war.

(This story has been refiled to clarify in lead that Acerp is the telecoms regulator not operator.)

By Mathieu Rosemain and Sybille de La Hamaide