(Adds analyst, source, shares)
By Stephen Jewkes and Valentina Za
MILAN, Dec 12 (Reuters) - Italian energy company Eni will sell a 30 percent stake in its giant Egyptianoffshore gas field Zohr to Russia's Rosneft for $1.575billion, pressing ahead with asset sales to fund investments andoffset weak oil prices.
Eni, which owns 90 percent of the Shorouk concessioncontaining Zohr, said Rosneft would pay $1.125 billion cash forthe stake and would reimburse investments already carried out byEni for around $450 million.
The deal comes less than a month after Eni's sale of a 10percent stake in Zohr to BP at the same implied price,bringing overall proceeds to around $2.1 billion.
Eni, whose cash flow fell 19 percent in the third quarterdue to low oil prices, pledged at the start of the year to sell7 billion euros ($7.43 billion) worth of assets to 2019 -- 5billion euros in the first two years.
"This is a great success for Eni to receive $2.1 billion fora year's work and have major partners to share the risk andcapex," said Bernstein oil analyst Oswald Clint.
At 1354 GMT Eni shares were up 4.2 percent while theEuropean oil and gas index was up 2.1 percent.
Oil prices rose as much as 6.5 percent on Monday after OPECand some of its rivals reached their first deal since 2001 tojointly reduce output, though are still well below values above$100 a barrel seen in 2014.
Selling down stakes in oil and gas fields it operates ispart of Eni's so-called "dual exploration" strategy to raisecash to fund development and support dividends. In the last fouryears, Eni has raised about $6.3 billion in this way.
Zohr, discovered by Eni in 2015, is the biggest gas field inthe Mediterranean with an estimated 850 billion cubic metres ofgas in place.
The approval process for development of the field wascompleted in February and first gas should be produced by theend of 2017.
In November, Eni Chief Executive Claudio Descalzi said hewanted to cut Eni's stake in Zohr to 50 percent.
Rosneft, like BP, has an option to buy a further 5 percentstake.
"We suspect BP and Rosneft will take the additional 5percent next year given the high return of this field," saidBernstein's Clint. ($1 = 0.9426 euros) (Additional reporting by Vladimir Soldatkin in MOSCOW; Editingby Mark Potter and Michael Urquhart)
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