Bulgaria's Prime Minister Kiril Petkov urged Europe on Thursday (28 April) to be "stronger" and find alternatives to Russian gas, during a visit to Ukraine.
Russia on Wednesday cut off gas supplies to Bulgaria and Poland, both EU and NATO members in a move Brussels described as "blackmail".
"We have to be stronger. We have to be tough," the Bulgarian prime minister said in Irpin, one of the commuter towns outside Kyiv where Moscow is accused of committing war crimes following its 24 February invasion of Ukraine.
Bulgaria has "alternative choices" to Russian gas flows, Petkov said, adding that: "If we are able to do it, everybody in Europe should be able to."
The President of the European Commission, Ursula von der Leyen, has said Warsaw and Sofia are now receiving gas from their EU neighbours.
Last year, Russia supplied 32% of the total gas demand of the European Union and Britain, up from 25% in 2009, according to the International Energy Agency, although the situation varies significantly from country to country.
Bulgaria is almost at 100% dependent from Russian gas supplies.
Petkov said Moscow, which wants countries to make their payments in rubles since its invasion of Ukraine, cannot be seen as a trusted supplier.
"Today we have to pay in rubles. Tomorrow it will be the price. The next day it will the quantities," he said.
"You either have a contract that you respect, or nobody respects you," he added.
Standing where alleged Russian atrocities were committed in Irpin, Petkov said Bulgaria stands with Ukraine and pledged to "provide all the help necessary."
Russian President Vladimir "Putin should realise that he cannot win this war," the Bulgarian politician said.
Petkov took the initiative for this visit in the context of tense relations with the Bulgarian Socialist Party (BSP), a member in the fragile four-way coalition. BSP strongly opposes Bulgaria sending arms to Ukraine.
In his delegation, Petkov invited politicians from the coalition members, but BSP rejected the invite.
Petkov is also in conflict with the country’s President Rumen Petkov on the same account.
Former Bulgarian ambassador to Russia Ilian Vassilev told EURACTIV.bg in an interview that by cutting gas supplies to Bulgaria, the Kremlin seeks to replace Petkov as Prime Minister.
(With additional reporting by Georgi Gotev)