Russia questions value of Nabucco energy pipeline

He added: "But then, it's up to the West, I would not tell the EU, to make up its mind how to deal with Iran. Either bomb Iran or buy its gas."

Mr Chizhov's blunt comments came only hours after Turkmenistan had agreed to supply 10 billion cubic metres of natural gas to the EU each year - something that should cut the energy-hungry bloc's dependence on gas from Russia.

"There have been some euphoric comments about Turkmenistan," the ambassador said, stressing that the volume agreed by the two sides is "not enough". In addition, he questioned the ability of Azerbaijan, another potential source, to fulfil the union's sharply rising energy demand.

The European Commission considers Nabucco to be "essential" to the EU as it is designed to bring gas from non-traditional suppliers via a new transport route.

The pipeline - connecting Turkey with Austria, via Bulgaria, Romania, and Hungary - would enable the transportation of gas from the resource-rich Caspian region to the European market.

Its capacity amounts to 31 billion cubic metres of natural gas per year. The bulk of the supplies are expected to come from countries such as Azerbaijan, Kazakhstan, Turkmenistan or Egypt.

The EU is also hoping to secure natural gas from Iraq, with Baghdad earlier this week pledging to provide five billion cubic metres of gas each year. The two sides are set to sign a so-called energy security memorandum of understanding in coming days.

In response to Mr Chizhov's statements, the commission said that a list of source countries was yet to be defined. It addmitted, however, that once the problems with Iran are solved, Tehran can be taken into consideration on the longer term.

Meanwhile, Moscow - the world's largest producer of natural gas - has been pushing for its own project, the South Stream pipeline. It should connect Russia's Black Sea coast and Italy, with Bulgaria, Greece, Hungary and Serbia already saying they will take part in the project.

According to the Russian ambassador to Brussels, there will be enough room for the South Stream, Nabucco and perhaps for another pipeline due to growing energy consumption in Europe - but only in the long run.

In the short run, the defining difference is that the South Stream can rely on real gas supply, whereas Nabucco does not have gas, Mr Chizov said.

The South Stream project is seen by some as a rival to Nabucco, with the European Commission saying "it is not promoting it actively" because the pipeline will bring more gas from Russia.

"The two projects are complementary, not contradictory," reads the commission's official line on the issue. The EU needs 80 billion cubic metres of natural gas per year on top of current consumption.

But some experts on EU-Russia energy relations have also suggested that Moscow has made a valid point.

According to Marco Giuli from the Brussels-based Centre for European Policy Studies, the Nabucco pipeline is "economically viable only with Iranian gas".

He cited political tensions in Central Asia, the proximity of Chinese market as well as the US' tough stance on Iran among those factors that cloud Nabucco's prospects.

Within the 27-nation EU, France and the UK seem to have the toughest position towards the Iranian regime, wanting to stop its nuclear ambitions not only through dialogue, but also via sanctions.

On the other hand, Italy's oil and gas producer ENI is set to undertake some investments in Iran - something, Mr Guili says has been endorsed by the country's outgoing as well as incoming political leadership.