Vladimir Putin is threatening to turn off gas supplies to Europe from today, if countries refuse to pay their bills in Russian currency.
Germany - which is heavily reliant on imports - is calling that "blackmail".
Negotiations aimed at ending the five-week war in Ukraine are to resume later.
Slovenia's prime minister, Janez Jansa thinks Russia needs Roubles to help prop up its struggling economy.
"The Russian economy depends more than 50% on energetics.
"It's not possible to find another country to sell them natural gas, for example, because the piplines are going to Europe."
