The planned Nabucco pipeline to bring natural gas from the Caspian region to the European Union, described as a "new silk road" for energy, will pass its first great test on Monday with the signing of a formal agreement between the governments along its 3,300km route.

The hugely ambitious project has been mired in political wrangling, with Turkey, where the pipeline will start, demanding 15 per cent of Nabucco's gas.