Milan, May 30 - Telecom Italia's board of directors approved a plan Thursday to put some of its domestic fixed-line assets into a separate company - the first step in selling off assets and paying down debt. Telecom Italia said the copper and fibre-line network assets, valued at as much as 15 billion euros, will be held in a new company, a piece of which could eventually be sold to state-backed fund Cassa Depositi e Prestiti (CDP). Such a sale would help raise funds for the heavily indebted telecom. Meanwhile, Telecom Italia continues to consider a proposal to merge its mobile operations with Hong Kong-based conglomerate Hutchison Whampoa. Its interest in Telecom had raised political red flags about too much foreign investment in the domestic telecommunications giant. Telecom Italia's board also said it would immediately inform Italy's telecoms regulator, which must approve the spin-off.