BELGRADE (Reuters) - Serbian oil company NIS, majority-owned by Russia's Gazprom Neft and Gazprom, is likely to get a last-minute, 30-day extension to its waiver from U.S. sanctions, the CEO of state gas company Srbijagas said on Thursday.

The previous waiver is due to expire at midnight, and if it is not extended NIS could face crude supply cuts. NIS operates the only oil refinery in Serbia, which has annual capacity of 4.8 million tons and covers most of the Balkan country's needs.

"There will be more delays of sanctions ... , but we cannot expect more than 30 days," Srbijagas CEO Dusan Bajatovic told Belgrade-based Pink TV.

He did not say how he knew this information. Bajatovic is a member of Serbia's co-ruling Socialist party and Srbijagas is also a trade partner of Gazprom.

NIS did not immediately respond to a request for comment.

As part of its January 10 sanctions on Russia's oil sector, the U.S. Treasury's Office of Foreign Assets Control gave Gazprom Neft 45 days to exit ownership of NIS.

On March 19, NIS sought a 30-day waiver of the sanctions, an extension of the first reprieve approved on Feb 27, to secure more time to find a solution with the Russian companies.

On February 26, Gazprom Neft transferred stakes of around 5.15% in NIS to Gazprom in an attempt to ward off sanctions.

The transfer follows a similar change in 2022 when the company avoided EU sanctions imposed on Russia over its invasion of Ukraine.

Gazprom Neft now owns 44.85% of NIS, while Gazprom has 11.3%. The Serbian government holds 29.87%, and small shareholders the rest.

NIS imports about 80% of its needs through Croatian pipeline operator Janaf, with the remainder covered by its own crude oil production in Serbia.