An impasse over Russian oil and imminent US sanctions has put Serbia at loggerheads with its traditional ally in Moscow.

Added differences over Russian gas supplies and Serbia's arms trade have ramped up the tensions, with Serbian President Aleksandar Vucic trading barbs with the Kremlin.

The root of the problem, and the most pressing issue, is the fate of Serbia's national oil company.

Russia's Gazprom and Gazprom Neft own more than half the shares of Petroleum Industry of Serbia (NIS). That has put the company in a tight spot, after US sanctions on NIS came into effect last month over its ties to Russia's energy industry.

Serbian Energy Minister Dubravka Djedovic Handanovic has told the BBC that NIS's Russian owners have now asked the US for a waiver, indicating they are ready to transfer control to a third party. But time is running out.

The immediate impact of US sanctions on NIS has been felt swiftly, as petrol stations have warned customers that Visa and Mastercard can no longer be used for payments. This is evident across Gazprom-owned service stations, forcing customers to adapt to cash-only transactions.

Despite operating both oil refineries that supply the majority of Serbia's fuel, NIS now faces critical shortages as sanctions have disrupted the supply chain. The flow of oil via the Janaf pipeline from Croatia has stopped, risking depletion of refining capacities before the end of November.

Countries in the Balkans like Bulgaria are making moves too; while neighbouring countries are seeking alternatives or nationalizing their energy resources, Serbia is caught between urgent needs and historical ties to Russia.

This energy standoff has not only caused immediate economic disturbances but has potential long-term ramifications for Serbia's political relationships and energy strategies.