The offer, which should be presented by early-September, would value Open Fiber 7.7 billion euros ($9.1 billion), including debt.

Macquarie approached Enel in June with an initial offer for its stake in Open Fiber, which is jointly controlled with Italy's state lender CDP, and talks between the two companies had been extended.

(Reporting by Giulio Piovaccari, editing by Giselda Vagnoni)