A diverse source of energy, from Caspian to potential North American sources, is needed for European security, the EU's energy commissioner said Tuesday.

The European economy gets about a quarter of its natural gas needs meet by Russia, though most of that runs through the Soviet-era transit network in Ukraine.

Maros Sefcovic, the commissioner in charge of energy in the European Union, said European energy security and Ukrainian reforms go hand-in-hand.

"It is therefore a common interest for both Ukraine and the EU to ensure Ukraine has a modern and functioning energy infrastructure," he said

The World Bank in February pledged $2 billion in funding to help Ukrainian economic reforms. The group said last week regional conflict has undermined investor confidence in Ukraine, though recovery is possible if peace takes hold and structural reforms reach to budget management and the energy sector.

"I remain convinced that Ukraine will and should continue to play an important role in ensuring Europe's energy security as a transit country," the commissioner said.

Sefcovic said during a keynote address before the European Court of Auditors that Europe itself has a near infinite capacity to produce renewable energy and technology, describing smart grids as "Europe's shale gas."

Members of the EU in October agreed to cut greenhouse gas emissions by 40 percent, increase the renewable energy footprint by 27 percent and enhance energy efficiency by 27 percent from a 1990 benchmark by 2040.

"Until we reach the day when we can rely more on renewables, we also need to diversify our suppliers of traditional energy sources," the commissioner said.

Azerbaijan is expected to emerge as a major player in the European gas sector once a series of new pipelines from the Caspian Sea start operations before the decade ends. Pro-trade lawmakers in the United States, meanwhile, said a trans-Atlantic partnership agreement would bring more shale gas to European borders.