(Bloomberg) -- Bulgaria is starting to collect revenue from a new tax on imports and transit of pipeline natural gas from Russia, a measure that has caused a regional furor over energy security as winter approaches. 

The government in Sofia expects to receive the first monthly payments from the levy over the next 10 days, according to Finance Minister Assen Vassilev. The tax, in effect since mid-October, is designed to boost revenue and curb Russia’s ability to fund its war in Ukraine. 

Whether it can achieve those goals is yet to be seen. Hungary, which relies on Russian gas transited via Bulgaria, has said the measure is illegal and wants the European Union to investigate. Serbia and North Macedonia have also voiced concerns. 

Russian energy giant Gazprom PJSC hasn’t said whether it intends to pay, raising questions about the measure’s effectiveness.

“Let’s hope it’ll happen,” Vassilev told reporters last week, speaking about Gazprom’s potential payment. “Let’s not speculate.”

Russia last year cut off gas for Bulgaria’s domestic supplies after the Balkan nation refused to pay for the fuel in rubles, which Moscow demanded after the start of the war. Still, Bulgaria remains a key transit route for Russian gas to the region. 

A Bulgarian extension of the TurkStream pipeline under the Black Sea — which Russia uses to bypass transit through Ukraine — is almost entirely occupied by Gazprom under a long-term contract.

Refusal to pay the tax — set at 20 lev ($11) per megawatt-hour — could lead to Bulgaria blocking or revoking the assets of companies that don’t pay, starting with bank guarantees, Vassilev said last month. The Bulgarian finance ministry and the grid operator, Bulgartransgaz, didn’t immediately respond to a request for comment.

“The immediate effect will be a pile-up of penalties, since it seems unlikely either the buyer or supplier will agree to bear the additional levy, at least for now,” said Alireza Nahvi, a gas analyst at Bloomerg New Energy Finance. “If there is a reduction of flows, this will lead to increased demand for alternatives like LNG or other regional supplies.”

Bulgaria, which received almost all of its gas from Russia prior to the war in Ukraine, now meets a third of its annual demand through a long-term contract with Azerbaijan’s SOCAR. It also gets liquefied natural gas from terminals in Greece and Turkey. Serbia is also working on an agreement with SOCAR, as well as on a new pipeline link with Bulgaria. 

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