Russia's relations with countries that host pipelines shipping oil and gas westwards, many former Soviet Union states, have been characterised by frequent disputes.
Georgia, which is in conflict with Russia over two separatist regions, has two pipelines crossing it, bringing oil and gas from Azerbaijan to Turkey.
They are the first routes to take Caspian energy to the West that bypass Russia and are particularly valued by the European Union, which is anxious to reduce its dependence on Russian energy.
The political and security risks generated by conflict could help Russia in its drive to deter Western investors from greater involvement in Caspian energy and to ensure future export routes go through Russia.
Previous disputes have included cuts in gas supplies to Ukraine and a halt in oil shipments to Belarus, both as a result of pricing disputes with Moscow.
The main transit states are:
Georgia
Georgia is the only transit route for Azeri oil and gas to the West that bypasses Russia.
The Baku-Tblisi-Ceyhan pipeline, led by BP, opened in 2006 and can pump up to one million barrels a day of Azeri crude to the Turkish port of Ceyhan.
The Baku-Tblisi-Erzurum pipeline takes gas from the Shakh Deniz gas field in the Caspian Sea to Erzurum in Turkey. The pipeline, jointly operated by BP and Statoil, began exports to Turkey in 2007.
Georgia's importance as a transit state will increase if Western companies invest in Turkmenistan's gas fields and look for an export route across the Caspian Sea by passing Russia.
Ukraine
Around 80% of Russia's gas exports to Europe pass through Ukraine.
Ukraine has long haggled over how much it pays Russia for gas, but the row came to world attention in January 2006, when it led Gazprom to halt supplies to Ukraine.
As a result, exports to Europe, which relies on Russia for 25% of its gas, were also affected.
The dispute was solved by Ukraine agreeing to pay roughly double for its gas.
Russia has made clear its strategy of trying to buy into infrastructure in transit states, but Ukraine has balked at the prospect. Its parliament last year passed a law to ban the privatisation, sale or lease of the country's gas pipelines.
For its part, Russia has proposed building the Nord Stream pipeline to Europe, bypassing Ukraine to the north.
Belarus
Around 20% of Russia's gas export to Europe flows through Belarus.
In addition the Druzhba - or Friendship pipeline - which passes through Ukraine and Belarus, supplies Europe with around 10% of its oil.
During a pricing dispute with Russia in January 2007, oil shipments through Belarus were halted for three days. Belarus has also clashed with Moscow over the price it pays for its gas.
Poland
Poland is a major transit country for Russian oil and gas exports to Europe. Both the Druzhba and the Yamal-Europe gas pipeline pass through Poland from Russia via Ukraine and Belarus.
In a dispute last year, Poland rejected a demand by Russian energy giant Gazprom for it to lower its fees for pumping Russian gas across Polish territory to Europe.
Along with other transit states, Poland is opposed to a Russian-German scheme to lay a pipeline under the Baltic Sea directly linking Russia and Germany, because of fears it would would allow them to be cut off from Russian supplies.
Turkey
Following various disagreements with Russia, Turkey has looked to diversify its import sources and has ambitions to be an energy hub, rather than a transit nation for Russia.
Turkey's state-owned Botas is part of a consortium led by Austria's OMV to build the Nabucco pipeline, which would transport gas from the Caspian, central Asia, reducing dependence on Russia.
The Blue Stream natural gas pipeline connects the Russian system to Turkey.
Russia, together with Italian oil company Eni has a project to extend Blue Stream to southern Europe through Turkey. It has also announced a 50/50 joint venture with Eni, known as South Stream, which would bypass Turkey.
The Baltics
The Baltic states of Estonia, Latvia and Lithuania serve as a vital transit location for Russian oil exports.
The Russian crude oil pipeline system is connected to three ports on the Baltic Sea -Latvia's port of Ventspils, Lithuania's port of Butinge and the Russian Primorsk.
Smaller quantities of crude oil and significant quantities of refined oil products are also distributed by rail to other Baltic ports, such as Tallinn in Estonia.
Estonia
Russian oil firms have been shipping 25m tonnes of refined oil products a year, a quarter of their exports, via Estonia, but volumes have fallen following a dispute with Moscow.
Shipments of other commodities, including metals and coal, through Estonia have also been reduced.
Relations deteriorated after Estonia in April last year moved a memorial to World War Two Red Army soldiers from a site in the city centre to a military cemetery, triggering two nights of riots by local Russia speakers.
Lithuania
In 2006 Russia shut the pipe to Lithuania's Mazeikiu refinery.
Analysts have linked the oil stoppage to Lithuania's decision to allow Polish company PKN Orlen to buy the refinery in which several Russian firms were interested.
Latvia
In 2003, Russia closed an oil pipeline to Latvia's Ventspils oil terminal. Russian officials have said Ventspils had little hope of recovering its crude supplies following Russia's expansion of Primorsk.
