Russia’s gas giant Gazprom seeks $50 billion from Ukraine’s Naftogas at the Stockholm Arbitration hearings and its claims can increase up to $80 billion, Group Chief Commercial Officer of Naftogaz, Yuriy Vitrenko said on Wednesday.

According to Vitrenko, Naftogaz demanded that Gazprom must pay $30 billion and the claim may reach about $50 billion.

“In accordance with the rule ‘take or pay’ Gazprom already demands $50 billion from us, will demand $30 billion more [till expiration of contracts], their total claim will be $80 billion,” Vitrenko said at the online conference, as quoted by the “Novoye Vremya Business” media outlet, according to Sputniknews.

Russia and Ukraine have been locked in a three-year row over the price of Russian natural gas and delivery terms.

In June 2014, Gazprom switched Ukraine to a prepayment scheme citing its massive gas debt. Ukraine’s energy firm Naftogaz refused to buy gas from Gazprom in October 2015 due to high prices, saying it had other suppliers in Europe.

The European Union intervened in late 2015 to ensure uninterrupted gas transit through Ukraine.