MILAN/MOSCOW (Reuters) - Russian state oil producer Rosneft (>> NK Rosneft' PAO) said Western sanctions had stopped it building up its stake in Italian refiner Saras, forcing it to sell the stake two years after buying it.

Russia's biggest oil producer agreed in 2013 to buy a 21 percent stake in Saras, which is 50-percent owned by Italy's Moratti family, in a move that was set to strengthen Rosneft's commitment to the Mediterranean area.

Rosneft, which had already sold 9 percent of its stake in 2015, sold the remaining 12 percent stake in accelerated book-building on Wednesday. The price was 1.53 euros per share, raising 175 million euros (151.9 million pounds), Rosneft said in a statement on Wednesday.

The statement confirmed an earlier Reuters report, citing market sources, on the price.

Rosneft has been subject to EU and U.S. sanctions since 2014, following Russia's seizure of the Crimea region of Ukraine. Chief Executive Igor Sechin, a close ally of Russian President Vladimir Putin, is himself under sanctions.

"The sale is part of a programme of optimising the company's portfolio of assets linked, in part, with the fact that it is impossible to implement the original agreement on increasing Rosneft's share to a controlling stake, given the sanction restrictions in force," Rosneft said in a statement.

"The money received from the sale of the share will be used to implement strategic projects with other Italian partners of Rosneft," the statement said.

The Saras investment was the latest in a series of cases of sanctions hampering Rosneft - though the company's bosses insist it is nevertheless able to flourish and do business with foreign partners.

In June 2013, Rosneft and ExxonMobil (>> Exxon Mobil Corporation) set up a joint venture to explore for oil in the Kara Sea, in the Arctic. But Exxon was forced to halt drilling there in 2014 after the imposition of sanctions.

A deal under which Rosneft was to acquire an oil trading business from Morgan Stanley, part of a drive to boost the Russian firm's global reach, was torpedoed by the U.S. authorities in 2014.

($1 = 0.9369 euros)

(Reporting by Stephen Jewkes, Andrea Mandala and Abhinav Ramnarayan; Writing by Valetina Za and Christian Lowe; Editing by Susan Thomas)

By Stephen Jewkes and Katya Golubkova