(Adds quotes from chairman on spin-off process)
MILAN May 9 (Reuters) - A proposed spin-off of Telecom Italia's domestic phone lines, its most valuable asset, that could open up the network to rivals would take time to execute, its chairman said.
Putting the fixed-line assets into a separate company could also pave the way for an eventual sale of a minority stake in the network, which is estimated to be worth 12-15 billion euros ($16-20 billion).
Splitting off the fixed lines would give all telecom operators equal access to the network - a European Union requirement - radically changing the Italian market, chairman Franco Bernabe said on Thursday.
The move could help Telecom Italia, Italy's biggest phone group by market share, free up resources to cut its more than 28 billion euros of debt and fund investment.
Telecom Italia's board will meet on May 23 to decide whether to go ahead with the separation.
"It's a complex process and will require a long time to be implemented," Bernabe told analysts on a conference call.
It was too early to say if any deal, which would have to be discussed with government and regulators, might be completed this year, he said.
Bernabe said Telecom Italia could sell a minority stake in the network to state-backed financing body Cassa Depositi e Prestiti (CDP) after a separation.
He ruled out the sale of a majority stake.
A deal with the CDP could help smooth a potential tie-up between the Italian firm and Hong Kong-based conglomerate Hutchison Whampoa because it would assuage government concerns about the national network falling into foreign hands.
He declined to comment on the possibility of a stock market listing for the network company.
($1 = 0.7591 euros) (Reporting By Danilo Masoni; Editing by Erica Billingham)