* Stake worth around 1.5 bln euros at market prices * Eni to give details on sale on Thursday * Eni will hold 8.5 pct of Snam via convertible bond MILAN, May 8 (Reuters) - Italy's Eni will sell an 11.7 percent stake in Snam, worth around 1.5 billion euros ($1.98 billion) at market prices, as it makes good on a pledge to exit the gas transport company. Eni said on Wednesday at the end of the sale it would own a 8.54 percent stake in Snam linked to a 1.25 billion euro convertible bond it placed in January. Last year the Italian government introduced a decree calling on the oil major to sell its controlling stake in Snam in an effort to improve competition in the gas sector and reduce gas prices. State-controlled financing company Cassa dei Depositi e Prestiti bought a stake of just under 30 percent of Snam in a deal that nets Eni 3.517 billion euros in cash and lifts around 11 billion euros of Snam debt off its balance sheet. The Italian government considers Snam's gas transport network and the power grid of Terna strategic assets and is keen for CDP to keep control of them. Eni said in a statement it would sell 395.3 million shares in Snam through an accelerated bookbuilding process, adding final details of the operation would be announced on Thursday. The shares will be placed with institutional investors JP Morgan and UniCredit as joint bookrunners, it said. Snam shares closed on Wednesday at 3.848 euros. Eni Chief Executive Paolo Scaroni has on several occasions said the company does not want to remain invested in listed companies it does not control.