(Reuters) – Russia will not change its contract price for gas exports in “unfriendly”, but payment must be made in the rouble equivalent at a preagreed settlement day as an option to swap the currency.

Russia’s number one producer has declared that Russia will soon be requiring “unfriendly countries” to pay fuel in rubles. The announcement raises concern about Europe suffering a gas crisis.

Sources said that “only the payment currency is changing,” while the contract currency was not. According to this source, payments for transactions in euros should be made at “official rouble/euro exchange rates” set by Russia’s central bank.

Sources said that the proposed scheme was one option and not the final. Gazprombank is Russia’s third largest bank and could be used as an intermediary to facilitate transactions between Gazprom buyers (MCX:).

A source familiar with the gas payments program told Reuters, “There’s no final decision yet. The work is ongoing.” Gazprombank, Gazprombank and the central bank did not respond to Reuters’ request for comment.

The question of whether or not gas buyers from the so-called unfriendly countries, those that joined Western sanctions on Russia, will be able to accept the request to pay in Russian rubles is still unclear.

Gazprombank, one of Russia’s main payment channels, is used to pay for oil and gas. This was done in conjunction with other Russian companies.

Germany activated an emergency plan Wednesday to manage gas supplies. This could lead to Europe’s biggest economy having to ration its power in the event that a dispute over Moscow’s demand of rouble payments causes disruptions or halts supply.

Putin will listen to suggestions on how to change the payments to rubles, from Gazprom to the central bank on Thursday. The scheme will then be publicized, Dmitry Peskov, a Kremlin spokesperson, said Wednesday.

Peskov explained that the customers are not required to convert to roubles immediately after Thursday’s announcement, because payments and delivery can take time.

Gazprom is responsible for 40% of European imports. However, Gazprom plans to increase its average price per 1000 cubic meters in the west this year from $280 by 2021.