MILAN, Feb 15 (Reuters) - Telecom Italia's (TIM) competitors have written to the Italian government to voice concerns about the risk that a planned spin-off of the former phone monopoly's network assets reinforces its dominant position in the fixed broadband market, a document showed.

In a letter dated Feb. 14 of which Reuters saw a copy, Vodafone, Fastweb, Iliad, Wind 3 and Comcast's Sky Italia drew attention to the terms of an agreement that regulates the relationship between TIM's remaining services business and the newly-created network company.

The letter said the two companies could retain a "strong vertical mutual dependence" which could hurt other players that, like TIM's services arm, also need to use the network to reach their final customers.

TIM plans to finalise later this year a sale, worth up to 22 billion euros, of its fixed-line network assets to U.S. fund KKR, subject to approval from the European Union antitrust regulator.

Earlier on Thursday, TIM CEO Pietro Labriola said he did not expect the deal to encounter any "specific" antitrust obstacles in relation to competitors' access to the spun-off network.

It was not immediately possible to get a comment from all the parties involved. (Reporting by Elvira Pollina; Editing by Valentina Za)