BELGRADE (Reuters) - Serbian oil company NIS, which is majority-owned by Russia's Gazprom Neft and Gazprom, has submitted a formal request to the U.S. Treasury Department for a waiver of sanctions for 90 days, Serbia's energy ministry said on Tuesday.

In a statement, the ministry said that the NIS request has the backing of the Serbian and Hungarian governments.

"We urgently request that OFAC (Office of Foreign Assets Control) consider immediate assistance, in the form of a suspension of sanctions for a minimum of 90 days, while a sustainable solution that would lead to the lifting of sanctions is considered," the statement said.

It also said that NIS's request concerns obtaining licenses that would allow it to continue operating while a solution to the ownership structure and management is sought.

"The (Serbian) government ... supports the request ... because sanctions would impair the company's ability to supply Serbian citizens with oil and oil derivatives," the ministry said.

Gazprom Neft and Gazprom have 50% and 6.15% stakes respectively in the company which operates the sole oil refinery in Serbia.

The Serbian government holds a further 29.87% with small shareholders accounting for the remainder.

On Jan. 10, Serbia's President Aleksandar Vucic said Russian companies were given 45 days to 45 days to exit their ownership in NIS and that any deal would have to be approved by OFAC.

On Jan. 14, Russian Foreign Minister Sergei Lavrov said that Moscow was in contact with Belgrade about NIS.

Serbia receives most of its crude oil through Croatia's pipeline operator Janaf, through which Hungary also imports some of its oil.

NIS, one of the biggest contributors to Serbia's state budget, had signed a contract with Janaf for the transport of 10 million tons of oil through Croatia from Jan. 1, 2024 until Dec. 31, 2026.

(Reporting by Aleksandar Vasovic; Writing by Angeliki Koutantou; Editing by Susan Fenton)