ROME, Nov 9 (Reuters) - Telecom Italia's (TIM) decision to sell its prized landline grid to KKR is a "milestone" move for the former phone monopoly and falls within the exclusive competence of the board, the head of the telecoms group said on Thursday.

CEO Pietro Labriola's comments follow criticism from top shareholder Vivendi, which has threatened a legal challenge to the plan to sell the grid, saying it considered the decision to proceed without a shareholder vote as "unlawful".

In a post-results call with analysts, Labriola said the decision to accept KKR's 19 billion euro ($20.3 billion) offer for its fixed-line asset without a shareholder vote "was based on several independent legal opinions indicating that the matter clearly falls within the exclusive competence of the board".

"It is not possible under the Italian law to transfer such competence to the shareholders," the CEO added.

According to Vivendi, the sale required an extraordinary shareholder vote because it would change TIM's corporate purpose and therefore required a change to the company bylaws.

Labriola rejected the argument, citing a "very careful and deep analysis of the deal on the basis of the effective perimeter of TIM's network".

"There is nothing in our bylaws asking for the ownership of the network. And so frankly, we are quite confident that our vision of the transaction will be confirmed even in court", he added.

Labriola said the deal is "no more than the strict execution of the delayering plan" unanimously approved in 2022.

Sources told Reuters that expectations are now for Vivendi to file a complaint with a Milan court in a bid to challenge the board decisions.

But TIM General Counsel Agostino Nuzzolo, speaking in the call with analysts, said that the company had not so far received any indication of a legal complaint filed with the court aimed at suspending the deal.

Labriola said that given the group did not foresee any "hurdles in the required approvals" nor a risk of the transaction being delayed or blocked, there would not be any changes in the timing of the closing of the deal, expected in the summer next year.

($1 = 0.9360 euros) (Reporting by Elvira Pollina; Editing by Giulia Segreti and Jan Harvey)