Gazprom, which supplies a quarter of Europe's gas needs, has been under EU investigation since September 2012 for suspected anti-competitive behaviour, including over-charging customers and blocking rival suppliers.

The company has been trying to settle the case by putting forward concessions since then. It has, however, resisted regulatory pressure to change its pricing practices in eastern Europe, which is the main concern of the EU regulators.

"Some work was done but was suspended because of the Ukraine crisis but this investigation will not stop," European Competition Commissioner Joaquin Almunia told an International Bar Association conference.

Europe's incoming competition commissioner Margrethe Vestager, who will take over from Almunia in November, will have to decide whether to continue the settlement talks, charge Gazprom with breaching EU rules or drop the case.

(Reporting by Foo Yun Chee; editing by Barbara Lewis and Jane Merriman)

By Foo Yun Chee