Nabucco pipeline deal signed

Countries involved in the Nabucco pipeline project signed an important deal moving things forward on this project.
The Nabucco pipeline has not been built yet, it is a project to bring Central Asian gas to Europe through Turkey, and is backed by the West but opposed by Russia. It is very significant as it would diversify Europe's energy sources and hence reduce Europe's dependence on Russia; therefore it would reduce the geopolitical leverage Russia has over Europe.
As Asia Times notes, Iran is an important player in the Nabucco pipeline as it could provide Europe with much natural gas. However the US is opposed to Iran joining the project until it behaves well, i.e. until it does what the US wants.
Also, Turkmenistan would be an important supplier of gas to the pipeline; this would hurt Russia again, as Russia would like to control Turkmenistan's gas reserves, not see them go directly to Europe.
So we'll see how those things play out...