The French firm, deemed strategic by the government for its high-tech assets such the manufacture of supercomputers, has yet to recover from a series of setbacks that wiped out close to two-thirds of its share price and led to the reshuffling of its top management.

French news website BFM Business reported earlier on Monday that Atos' major announcement at its investor day on Tuesday would concern the carving out of its low-margin and declining IT infrastructure management services into a single legal entity.

The move would aim to facilitate the reorganisation and cost management of this large set of activities, BFM Business reported. Atos declined to comment.

The news sent shares down as it highlighted a lack of progress made on the planned sale of part of these regrouped assets. Atos said last year it was seeking investors for non-strategic assets representing 20% of its total revenue.

"Once you say I want to sell, it's non-strategic, it has to materialize quickly, otherwise you end up thinking there's no buyer," an analyst said.

An industry source agreed, saying: "Markets were still hoping that tomorrow's capital market day would be the opportunity to announce talks were under way for these assets."

Reports of differing views between the new CEO Rodolphe Belmer and Atos' chairman Bertrand Meunier over strategy was also weighing on shares, Societe Generale said.

Two sources close to Atos confirmed that tensions have surfaced lately between the group's board and Belmer.

"This could reduce the credibility of the CEO and challenge his authority internally, forcing him to do things he does not believe in, which is never a good thing, in our view," Societe Generale said in a note to clients.

(Reporting by Mathieu Rosemain; editing by David Evans)

By Mathieu Rosemain