"We need clarity and we need rather detailed guidelines from the European Commission on possible payment solutions. What we need from the European Union is clarity," Catherine MacGregor told a news conference on renewables.

Russian President Vladimir Putin has demanded payments for the country's gas in roubles in response to sweeping Western sanctions against Russia after its invasion of Ukraine.

Moscow has notably said that foreign gas buyers must deposit euros or dollars into an account at Gazprombank, which would convert them into roubles.

Russia cut off gas supplies to Poland and Bulgaria last month after they refused to pay in roubles under the new arrangement, raising fears that other countries could be next.

MacGregor earlier told RTL radio that Engie was "still paying in euros" and working on a solution to Moscow's demands, adding that Engie's stocks are currently "rather full".

MacGregor said that a halt in Russian gas supplies to Europe was a "credible" scenario and that the main unknown was whether Russia would cut its gas supplies to Europe "before or after summer".

There are "no worries" over supplies to its clients in May, she added, because the next payments are due by the end of the month.

"What is important is to anticipate next winter. That is why the timing of a halt is key. The bigger our stocks, the easier we will go through next winter," she said.

Engie, like other European companies in the sector, is preparing for an eventual halt to Russian gas supplies to Europe, diversifying supply sources and "massively" importing Liquefied Natural Gas (LNG).

The company recently sealed a 15-year LNG deal with United States-based NextDecade Corp.

Longer-term expansion in renewables is another part of Engie's response, MacGregor said.

Russian gas accounts for 20% of Engie supplies and for 40% of Europe's gas needs.

The European Commission on Monday said that compliance with Russia's proposed rouble payment scheme in full would breach existing EU sanctions against Russia but promised more detailed guidance on what companies can and cannot do legally.

(Reporting by Tassilo Hummel and Dominique VidalonWriting by Sarah Morland, Dominique VidalonEditing by David Goodman and Jane Merriman)

By Dominique Vidalon and Tassilo Hummel