BELGRADE, May 7 (Reuters) - Serbia will not allow a recently formed local company to purchase a majority stake in its Russian-owned NIS oil firm because it lacks expertise, President Aleksandar Vucic said on Thursday.

A company called KFT Senator Treasury G.T.7 Two LLC (Senator) - founded just last August and run by a local businessman, Ranko Mimovic - said on Wednesday that it offered to purchase a 51.16% stake in NIS from Russia's Gazprom Neft SIBN.MM and Gazprom GAZP.MM for 2 billion euros ($2.35 billion).

The bid would represent a challenge to Hungary's MOL MOLB.BU, which is negotiating the purchase of a majority stake in NIS, a key condition for the United States to lift sanctions on the company that operates Serbia's only oil refinery.

"He's (Mimovic) never dealt with (crude oil processing) in his life, and now he’s going to buy it (NIS) ... Serbia won't allow it," Vucic told reporters in Belgrade.

The U.S. Treasury's Office of Foreign Assets Control (OFAC) imposed sanctions on NIS last October, as part of wider measures against Russia over its war in Ukraine, and demanded the divestment of shares owned by the Russian companies.

In a statement on Wednesday, Gazprom Neft said it was actively preparing to sell its stake in NIS to MOL and that it was not negotiating with anyone else.

Gazprom holds an 11.3% stake in NIS, while Gazprom Neft owns 44.9%. The Serbian government owns 29.9%, with the remainder held by small shareholders and employees.

($1 = 0.8503 euros)

($1 = 99.6300 Serbian dinars)