Some of Europe’s largest energy companies are preparing to use a new system of paying for Russian gas in rubles, which critics believe will undermine EU sanctions, the Financial Times reports.

Among the companies planning to use ruble accounts for gas payments are Germany’s Uniper and Austria’s OMV, while Italy’s Eni is weighing all possible options.

Gas distributors in Germany, Austria, Hungary and Slovakia plan to open ruble accounts at Gazprombank in Switzerland to meet Russia’s demands for ruble-denominated gas payments.

Negotiations between European buyers and Russia’s state-owned gas supplier Gazprom have intensified as payment deadlines approach.

At the same time, Italy’s Eni, another major Gazprom customer, is still evaluating its options. Italian officials say the Rome-backed company has until the end of May, when its next payment for gas supplies from Russia is due.

In late March, Russian President Vladimir Putin issued a decree requiring gas buyers from “unfriendly” countries, which include all EU countries, to open bank accounts with Gazprom’s Swiss-based financial and trading arm to pay for gas supplies. The measure is seen as a way to neutralize EU sanctions against Russia’s central bank.

Gas importers from Poland and Bulgaria, which refused to sign up to the scheme proposed by Moscow, did not receive gas from Russia on Wednesday. Ursula von der Leyen, the president of the European Commission, called the decision tantamount to blackmail.

The European Commission issued official technical guidance to EU countries that acknowledges Moscow’s financial scheme could be “sanctions-compatible” under certain conditions and would result in Russia being able to generate billions in gas revenues to support the ruble and its economy.

Under the proposed scheme, European gas companies would continue to pay Gazprombank for imports in euros, then the Russian bank, which is not under EU sanctions, would convert their euro deposits into rubles in a second account opened in their name for later payment at their request.

European Commission advisers have concluded that any move by the EU to impose sanctions on Gazprombank – which would be the quickest way to close the loophole – could jeopardize the entire existing mechanism for paying for Russian gas, leading to a catastrophic cutoff of supplies to the bloc.

According to Valdis Dombrovskis, executive vice president of the European Commission, the implementation and interpretation of the contracts falls primarily on the shoulders of individual companies that signed contracts with Gazprom, rather than on EU countries. But they must adhere to the letter of those contracts.

“Prices are agreed in euros or dollars. So you pay this amount in euros for a certain amount of gas and that’s the end of it,” he said.

He acknowledged that Russia’s actions to cut off gas supplies to Bulgaria and Poland were nonetheless a problem.

Each company, meanwhile, interprets its options differently: for example, Tiina Tuomela, Uniper’s chief financial officer, said: “We believe that the change in the payment process is in line with the sanctions regulations, so payments are possible.”

Italian officials said the European Commission’s advice on whether the payment scheme through Gazprombank constituted a sanctions violation was ambiguous and did not provide clarity to member states.

And German Vice Chancellor and Economy Minister Robert Habeck said Wednesday that the Russian payment mechanism is “a path that the EU has outlined for us that is compatible with the sanctions and, as far as I understand, the German companies that are doing this are honoring their contracts.”