Turkey piled more doubt on the future of the Nabucco gas pipeline, linking its participation in the project to its future accession to the European Union, world news agencies reported.

Turkish prime minister Tayyip Recep Erdogan, who began a three-day visit to Brussels on January 19, has said that should talks on the accession chapter on energy remain blocked, "we would of course review our position."

EU has been promoting Nabucco as an alternative source of gas to deliveries from Russia, meant to supply the bloc with 30 billion cubic metres of gas from the Caspian Sea. In light of the ongoing entanglement between Russia and Ukraine, which resulted in a complete shutdown of gas deliveries to EU countries, the need for diversification has resurfaced with greater intensity.

Nabucco has caused some controversy amongst analysts, not all of whom are convinced it was a feasible alternative, as doubts persist over whether enough gas can be secured for the pipeline to make the eight billion euro project worthwhile.

Pierre Noel, an energy analyst at the European Council on Foreign Relations, has claimed that the concept was flawed, saying that "[European bureaucrats] think you can build a pipeline and then the gas will flow. It's simply not credible," as quoted by The Guardian newspaper.

The pipeline remains at the drawing-board stage, mainly because it appears to be a highly risky business calculation. Construction has already been pushed back from 2008 to 2010, and even that date remains far from certain.

So far, only three billion cu m has been sourced for the pipeline, Reuters reported, compared to a bare minimum of 15 bcm needed to get it started.

Erdogan echoed the skeptics, saying: "The information is that the countries that say that they will provide sufficient amounts of natural gas do not have enough natural gas to provide."

Sofia is scheduled to host an international conference on the future of Nabucco, organised by the Bulgarian Presidency, in spring 2009.