Gazprom, the world's top gas producer, has been under regulatory fire since September 2012, for allegedly over-charging customers in eastern Europe, blocking rival suppliers and hindering the free flow of gas across some EU countries.

The company said earlier this year that it was keen to settle the case, warding off a possible fine of as much as $13.6 billion but discussions with the European Commission have stalled over the issue of what constitutes appropriate pricing.

European Competition Commissioner Joaquin Almunia told European lawmakers that he was preparing a so-called statement of objections, or a charge sheet, which sets out suspected violations of EU rules for Gazprom.

Almunia, who is scheduled to leave office at the end of October, did not say when he would send the document to Gazprom. The company can ask for a closed-door hearing to defend its case.

(Reporting by Foo Yun Chee; editing by Philip Blenkinsop)