MILAN/SAO PAULO, Aug 7 (Reuters) - Latin American fibre optic network company Ufinet, owned by Enel and private equity firm Cinven, has made a non-binding offer for the fibre unit of Brazil's Oi, two sources familiar with the matter said.

As part of its restructuring plan to exit bankruptcy protection, The Brazilian telecoms company aims to sell up to 51% of fibre infrastructure unit InfraCo to fund its expansion.

Ufinet, a wholesale operator of fibre telecoms networks, has more than 70,000 kilometres (43,500 miles) of optical cable networks in Latin America, including Brazil.

Enel, Europe's biggest utility, owns 21% of the company but has joint control with Cinven, which owns the remainder. Enel has options expiring end-2021 to take full control.

"The deal makes sense for Enel since it has grid assets in Brazil and can leverage the fibre-optic network," a banker close to the matter said.

Enel, which has placed digitalisation at the heart of its strategy, is one of the biggest foreign power grid operators in South America where it also has green energy operations.

In Italy it owns half of Italy's Open Fiber which is rolling out fast broadband across the country.

Besides Ufinet, an infrastructure fund managed by Banco BTG Pactual SA and Highline do Brasil, a portfolio company of U.S. private equity firm Digital Colony, are also among the bidders for Oi's fibre unit, sources said.

A report by Brazil's Exame this week said any InfraCo deal could involve an overall layout of 11.5 billion reais ($2.2 billion), including a capital increase.

Enel and Cinven declined to comment.

($1 = 5.3315 reais) (Reporting by Stephen Jewkes in Milan and Carolina Mandl in Sao Paulo, editing by Louise Heavens)