BELGRADE, June 3 (Reuters) - Hungary's largest oil and gas corporation, MOL MOLB.BU, has asked the U.S. government for a one-month extension to complete talks to buy a majority stake in Serbia's NIS NIIS.BEL, an oil company controlled by Russia, Serbia's energy minister said on Wednesday.

The request comes ahead of a June 6 deadline following a two-week extension which MOL secured last month to finalise negotiations with Russia’s Gazprom Neft SIBN.MM over its planned purchase of a 56.16% stake in NIS.

NIS is subject to U.S. sanctions imposed in October over its Russian ownership, part of broader measures targeting Moscow’s energy sector following its invasion of Ukraine. Washington has pushed for the divestment of the Russian stake.

"MOL has asked OFAC (Office of Foreign Assets Control) for additional time to complete negotiations on NIS sale," Serbian Energy Minister Dubravka Djedovic Handanovic said after a meeting with Gazprom Neft CEO Alexander Dyukov in St Petersburg.

"They have asked for additional 30 days to complete negotiations," Handanovic said in a statement.

She said that Dyukov had said that NIS would also ask the U.S. for an extension of an operating licence which is due to expire on June 16.

MOL said on January 19 it had signed a binding agreement with Gazprom Neft and Gazprom GAZP.MM to buy their combined stake in NIS. It did not disclose the price.

Serbia holds a 29.9% stake in NIS while the remainder is held by minority shareholders.

Belgrade and MOL must also agree on the company’s future operations before the transaction can be completed. NIS runs Serbia’s only oil refinery, making it central to the country’s energy supply.