"We don't know yet what it will be - either new legislation or guidelines or whatever. We are still in the impact assessment phase where the decision has not been entirely taken," the commissioner, attending a meeting of EU environment ministers, told journalists in Vilnius.
The European Union's executive arm will present a proposal on safety standards by the end of this year, Potocnik says, adding that the Commission "is not at all interfering with the individual decision of the member state what will be their energy mix."
Lithuanian Minister of Environment Valentinas Mazuronis said that EU ministers were scheduled to discuss shale gas regulation at a meeting in Vilnius later in the day.
Large-scale shale gas production takes place in the United States, but European countries have different positions on the issue. Critics say hydraulic fracturing used for the extraction of shale gas may cause huge environmental damage.
The Government of Lithuania is yet to decide whether to allow US company Chevron to explore for shale gas in Western Lithuania. Supporters say shale gas extraction would be an alternative to Russian gas and would bring economic benefit to the state.