Enel SpA (ENEL.MI) mulls merging its Spanish renewable assets with those of its Endesa SA (ELE.MC) unit to form a new renewable company owned by the Italian utility, people familiar with the matter said Thursday.

If a possible deal is concluded, the assets will be majority-owned by Enel Green Power SpA, said the sources, who asked not to be named. The assets won't be sold separately to investors, one of the people said.

Enel plans to sell a minority stake in Enel Green Power this year, Chief Executive Fulvio Conti said last week. Enel became Europe's most indebted utility after an international acquisition spree that included the takeover of Spain's Endesa, in which it now owns 92%.

The Italian utility has pledged to cut its net debt to EUR45 billion by the end of this year from the EUR51 billion of last December, aided by the Enel Green Power sale.

Enel's renewable assets in Spain are held in an equally- split joint venture, called Eufer, with Spanish energy company Gas Natural SDG SA (GAS.MC).

It isn't fair to assume that the Eufer venture will be split should the Spanish renewables integration happen, one of the sources said.

In any case, Gas Natural has no intention to sell its 50% stake in Eufer to Enel, another source said.

Gas Natural lags behind other Spanish utilities in the very lucrative generation of renewable power in Spain, which has priority over other sources and gains hefty subsidies.

Last year, renewables excluding hydroelectric power only represented 6.4% of Gas Natural's electricity output, which is heavily dominated by gas-fired production.

However, due to the economic downturn and a surge in renewable power, Spanish gas-fired power stations in 2009 operated well below their generation capacity, leading to a 22% plunge in Gas Natural's output from natural gas last year.

Earlier Thursday, Endesa said it is studying with Enel the possibility of combining their renewable energy assets. It added no decision has been taken.