Writes through with additional details, context

BELGRADE, June 17 (Reuters) - The U.S. Treasury's Office of Foreign Assets Control (OFAC) has extended a licence to Hungary's energy company MOL MOLB.BU to negotiate the purchase of a majority stake in Serbia's Russian-owned NIS until July 1, Serbian news agency Tanjug reported on Wednesday.

The report offered no further details, and MOL did not immediately reply to a request for comment from Reuters.

OFAC imposed sanctions on NIS NIIS.BEL in October as the U.S. targeted Russia's energy sector over the war in Ukraine, and demanded that Russian firms divest the NIS shares they own.

MOL signed an agreement in January to buy the combined 51.56% stake held by Gazprom Neft SIBN.MM and Gazprom GAZP.MM, pending OFAC approval.

U.S. sanctions forced NIS, which owns the only refinery in Serbia, to seek waivers from OFAC to buy and process crude oil, which would not be required once a share sale is completed. Late on Tuesday, OFAC granted NIS a sanctions reprieve until July 1.

Also on Tuesday, MOL signed a shareholders' agreement with Serbia over its 29.9% stake in NIS, separate from acquisition talks between MOL and Russian companies.