Last week, the Russian energy ministry rejected an EU proposal to hold a trilateral gas meeting on September 20.
The previous discussions, launched on May 2, that involved Oettinger, Russian Energy Minister Alexander Novak and his Ukrainian counterpart Yuriy Prodan, ended on June 16 with no result.
After Russia and Ukraine failed to reach a compromise on the gas issue, Naftogaz and Gazprom filed mutual claims to the Stockholm Arbitration Tribunal.
Ukraine currently does not receive Russian gas over an unsettled dispute over gas prices.
Ukraine's Naftogaz stopped paying for the consumed Russian gas since March 25. As of August 1, the overall debt of Naftogaz to Gazprom for supplied gas totaled about $5.296 billion.