A claim by Russia’s Gazprombank on about 40 percent of the gas in Ukraine storage is set to be foiled as state-run NAK Naftogaz Ukrainy says it has only a fraction of the fuel.

Gazprombank claims the 5.68 billion cubic meters of gas as backing for a $842.5 million loan to chemical producer Ostchem Holding Ltd. controlled by Ukrainian billionaire Dmitry Firtash.

Firtash was detained this year in Vienna on a U.S. warrant for charges including bribery, which he denies. Gazprombank has demanded early repayment of the loan by Dec. 30 because of Ostchem’s inability to meet its obligations, the Russian lender said on Dec. 15.

“Companies that are part of Ostchem store some gas” in the underground storage of Naftogaz’s transit unit Ukrtransgaz, the subsidiary said late yesterday in an e-mailed statement.“The residual amount of gas belonging to those companies are strictly recorded after their requests have been met.”

While the companies wouldn’t divulge how much of Ostchem’s gas is still stored, Naftogaz owned 11.45 billion cubic meters of the total 13.9 billion cubic meters in Ukrainian storage as of Dec. 1, according to the government-owned gas company.

The dispute over stored gas is the latest conflict between parties in Russia and Ukraine over the fuel. Russia cut supplies to Ukraine in June over a price and debt dispute after annexing Crimea and stoking unrest in two eastern regions of the country.

Firtash got the Gazprombank loan last year to buy 5 billion cubic meters of gas, paying $268.5 per thousand cubic meters of the fuel, compared with the rate of about $400 Naftogaz was paying.

The billionaire’s Group DF, which controls Ostchem, declined to comment when called by Bloomberg News.

Firtash made his fortune as a broker of Russian gas sales to Ukraine. He and a partner owned half of RosUkrEnergo, which became Ukraine’s sole gas importer from 2006 to 2009, a period bracketed by price disputes with Russia that led to supply halts. Ostchem has four chemical plants in Ukraine.