* Telco to write down value to 1.2-1.0 euros, sources say
* Telecom Italia board meeting Monday on media unit sale (Recasts lead, adds sources)
MILAN, Feb 18 (Reuters) - Telco, the holding company that controls Telecom Italia, is gearing up to write down its 22.45 percent stake in the Italian telecoms company by at least 20 percent, two sources close to the situation said on Monday.
One of the sources said the price of the shares on Telco's balance sheet should be marked down from a current book value of 1.5 euros to 1.0 euro each.
But a second source said the final size of the markdown would depend on a writedown Telecom Italia intended to make on goodwill.
"There's no decision yet but it looks to me like we could be heading for a writedown to around 1.2 euros," the source said.
Shares in Telecom Italia closed on Monday at 0.62 euro.
Telco is 46.2 percent owned by Spain's Telefonica, while Italian banks Mediobanca and Intesa Sanpaolo hold 11.6 percent each and insurer Assicurazioni Generali has 30.6 percent.
The board of Telco is due to meet on Tuesday.
Telco shareholders all declined to comment.
Two other sources familiar with the matter said Telecom Italia had launched an impairment test on goodwill relating to deals done in the last decade, when asset prices were higher.
"The outcome will be announced at the next board meeting which will examine final results," one of the sources said.
The second source said that while a decision would be made in March, an indication of the size of the writedown could be given on Monday evening.
Telecom Italia was not immediately available for comment.
Telecom Italia's board is meeting on Monday to discuss the sale of its broadcasting unit Telecom Italia Media. A statement is expected later.
The board of Telecom Italia is due to meet on March 7 to discuss final 2012 results.
In 2011, Telecom Italia carried out a goodwill writedown of 7.3 billion euros ($9.75 billion).
"A writedown of more than 2 billion euros is expected," said Oriana Cardani, analyst at Centrobanca.
Another analyst said there would be no consequences from the writedown since it would be an accounting operation with no cash outlay. ($1 = 0.7490 euros) (Reporting by Stefano Rebaudo and Stephen Jewkes; Editing by Luca Trogni, David Cowell and Dale Hudson)