The European Commission laid out plans Wednesday to cut the EU's costly reliance on energy imports, especially from Russia which has threatened to halt gas supplies to Ukraine, a key transit point for Europe.

A report prepared for European Union leaders recommended a broad series of measures to promote indigenous sources, including renewables and nuclear energy, and to make progress on a single energy market.

"Improving the internal market will mean that energy prices will be roughly the same everywhere," EU Energy Commissioner Guenther Oettinger said.

As for supply of gas, "we must move away from a monopoly supplier, Russia in this instance," Oettinger told a press conference.

Russia accounts for nearly 40 percent of EU gas imports, with half of that transiting through pipelines in Ukraine, according to Commission figures.

As the Ukraine crisis has deepened, Moscow has threatened to cut supplies -- as it did in 2006 and 2009 -- unless Kiev pays for deliveries up front.

The fear is that this would once again badly expose onward European countries, some of them totally dependent on Russia for natural gas.

EU leaders and official have suggested there could be a 'European Energy Union,' a single market complete with assured supplies and infrastructure to ensure the EU does not rely overly on any one country and so leave itself open to energy blackmail.

"We want strong and stable partnerships with important suppliers but must avoid falling victim to political and commercial blackmail," Oettinger said.

Accordingly, the EU must "complete the internal energy market, improve our infrastructure, become more energy efficient and better exploit our own energy resources.

"Moreover, we need to accelerate the diversification of external energy suppliers, especially for gas," he said.

The Commission said that in 2013, Russia accounted for 39 percent of EU gas imports by volume, with Norway on 33 percent and North Africa 22 percent.

In all, the 28-nation bloc depended on energy imports for more than 50 percent of its needs, a dangerously high level when global demand was expected to grow 27 percent by 2030, it said.

It put the import bill at more than one billion euros a day in 2012.

Business groups welcomed the Commission report.

"The situation in Ukraine is a wake-up call for a strong European energy security strategy ... (the report) ... rightly pushes for an increase and diversification of energy sources both domestically and externally," BUSINESSEUROPE said.

For its part, environmentalist group Greenpeace said the EU should not miss the opportunity to move the economy away from fossil fuels.

"Throwing money at new gas infrastructure to get Europe off Russian gas will not cure the addiction to imported fossil fuels," it said.

"Instead, Europe should kick the habit and exploit the enormous potential for energy savings and home-grown renewables by setting ambitious targets for 2030."

The Commission report is to be submitted to EU leaders at their end-June summit.