MILAN—The chances of the U.S. fund KKR pushing ahead with a firm bid for Telecom Italia (TIM) faded, with the two sides deadlocked on Tuesday over access to the company’s books. KKR has told TIM it cannot confirm its 10.8 billion euro ($11.9 billion) bid unless Italy’s biggest telecoms group provides access to its data under a due diligence process, according to two sources with knowledge of a KKR letter to TIM’s board. TIM, which is pushing ahead with its own standalone plan, wants to give the fund access only once a formal bid is made. KKR said in its letter it remained interested in buying TIM but would not confirm a bid without a due diligence as the war in Ukraine had changed market conditions, the sources said. TIM has cut its outlook and suffered a series of credit rating downgrades. The letter said KKR remained available to assess …