The mobile and broadband provider has entrusted the sale of Zeleris, which operates around the world and employs 1,200 people, to consultancy firm Ernst & Young, which valued the asset at up to 100 million euros ($121 million), said the source, who is familiar with the logistics sector.

A spokesman for Telefonica declined to comment. Ernst & Young was not immediately available for comment.

If realised, the divestment would represent another step towards reducing Telefonica's high debt following the sale of its mobile mast business, Telxius, to American Tower for 7.7 billion euros earlier this year.

Telefonica's strategy has so far included signing on investors in its Brazilian, Chilean and German businesses, swapping its data centres for equity, and joining its British brand O2 with Virgin Media in a 31.4 billion pound merger ($44.28 billion).

Last week, Telefonica's quarterly results prompted relief among investors, although CFO Laura Abasolo told analysts that up to 1 billion euros of the Telxius sale proceeds would go not to reducing debt, but paying future rental contracts for the mobile towers.

($1 = 0.8232 euros)

(Reporting by Clara-Laeila Laudette; Editing by Kirsten Donovan)