BELGRADE, July 31 (Reuters) - hold

Serbia secured another sanctions waiver from the United States for its Russian-owned oil company NIS, energy minister Dubravka Djedovic Handanovic said on Friday, allowing the firm that supplies most of the country's fuel demand to continue importing crude oil until August 28.

The waiver granted by the U.S. Office of Foreign Assets Control (OFAC) gives NIS, which operates Serbia's only oil refinery, more time while Hungary's oil and gas firm MOL negotiates the purchase of the Russian majority stake in the company.

"Thirty days is good news; NIS will have time to purchase and bring in enough crude oil,"Djedovic Handanovic said in a live broadcast on state RTS television.

On Friday, President Aleksandar Vucic said he hoped MOL would complete the  purchase of NIS in the coming days.

"We are expecting finalization of the deal in the coming days, I will probably speak with (the Russian President Vladimir) Putin and (Hungary's Prime Minister) Peter Magyar," Vucic told reporters during a trip to southern Serbia. 

The United States imposed sanctions on NIS in October as part of broader measures targeting Russia's energy sector over the war in Ukraine, and demanded divestment of Gazprom Neft and Gazprom, its Russian majority owners.

NIS's refinery in Pancevo, just outside the capital Belgrade, covers around 80% of Serbia's demand. It imports crude oil via Croatia's Janaf oil pipeline.

Other fuel imports to the Balkan country fell to 25% of their monthly target for July as record-low water levels on the Danube River forced barges and tankers to operate at a quarter of their cargo capacity. 

In January, MOL signed a provisional agreement to buy a combined Gazprom Neft and Gazprom 56% stake in NIS. The Serbian government owns 29.9% of NIS, with the remainder held by small shareholders and employees.

(Aleksandar Vasovic; Editing by Sanjeev Miglani)