Since its inception in 2002, the Nabucco natural gas pipeline has undergone a number of transformations, most recently into a much shorter link designed to carry Azeri gas from the Turkish border into southern and central Europe. 

But in the last ten years, its shareholder structure has remained much the same -- ostensibly the national companies of each of the states it will pass through. 

At present, the six equal shareholders in Nabucco -- or more correctly Nabucco West as the shorter project became known earlier this year -- are Austria's OMV, Hungary's MOL, Romania's Transgaz, Bulgarian Energy Holding, Turkey's Botas and Germany's RWE. 

RWE joined in February 2008, but is now set to leave, uncertain of the economic benefit of being a consortium member. 

But that could be the least of the changes about to take place. In August, the head of OMV said he did not expect the shareholder structure to remain the same in the future, hinting at the entry of new partners. 

Gerhard Roiss said there should be more of an upstream element to the shareholder group, turning the consortium into a more traditional mix of producers and transporters. 

Only OMV and MOL have upstream operations in the Caspian region, from where Nabucco's gas would be sourced. 

But now talks are underway that would see partners from the giant Shah Deniz field in Azerbaijan -- the much publicized source of the first gas that would flow through Nabucco -- join the group. 

"The shareholders are in negotiations with the Shah Deniz consortium and the negotiations are progressing well," a spokesman for Nabucco said Friday. 

"It would be inappropriate to comment further at this stage. The project continues to make sustained progress and is now in its advanced stages of development," he said. 

BULGARIA SPILLS THE BEANS 

The cat was let out of the bag earlier that day by the head of Bulgarian Energy Holding, Mihail Andonov, who said the Shah Deniz partners -- which comprise among others BP, Statoil, Total and Lukoil -- were eyeing a 50% stake in the pipeline. 

"Such a deal will boost significantly the prospects for Nabucco," Andonov was quoted as saying by French news agency AFP. 

It is the first time a number has been put on a possible stake for the Shah Deniz partners. 

In August, Roiss said only that the group would have a "different structure from today." 

"We have always said that upstream countries should be part of Nabucco. You can take it that the final ownership structure will be different," he said. 

Nabucco West is up against the Trans-Adriatic Pipeline to compete to carry Azeri gas from the European border with Turkey into European markets. A decision is due early next year on which pipeline will be chosen. It is not out of the question that both will eventually be built -- one to serve markets in central Europe and the other for southeast Europe. 

But it is almost certain that one will be built, and Azeri gas will be burned at some point in countries like Bulgaria and Hungary.