The West and Russia are battling for control of the transport of natural gas through the Balkans, as both sides pursue their geopolitical agenda in the volatile region.
Moscow has suffered a series of setbacks in the Balkans.
Montenegro has joined NATO, while Macedonia's new social democratic government seems to be distancing itself from its previous pro-Russia stance.
But while the West can offer Balkan countries incentives such as the prospect of membership of the European Union or investment locally, Russia can play the energy card.
Gas accounts for a quarter of the European Union's energy consumption and in 2016, Russia's Gazprom supplied a third of Europe's gas.
And in the Balkans, dependence on gas looks set only to increase as coal-fired power stations shut down -- under pressure from the EU.
Croatia is already an EU member, but the other so-called Western Balkan countries -- Albania, Bosnia, Macedonia, Montenegro, Kosovo and Serbia -- are all at different stages on the path to joining the bloc.
"In Serbia, Bosnia, Bulgaria and Macedonia, Russia tries to convert dependence on gas supplies into political dependence, and obstruct their integration with the West," said Timothy Less, head of the Nova Europa political risk consultancy.
Nevertheless, for the moment at least, Russian influence in the Balkans' energy sector is limited by a lack of infrastructure.
Without gas pipelines, it cannot supply most of the countries in the region, said Less. And it is here that the West hopes to steal a march on Moscow by backing rival projects.
- Battle of the pipelines -
The competing interests of the West and Russia in the Balkans gas market only serve to increase the geostrategic importance of the region.
"Southeast Europe lies at the crossroads of energy corridors linking East and the West," Albania's former foreign minister Paskal Milo told AFP.
"The region does not interest them as an economic resource, but it is becoming more important as a transit territory for other strategic markets in Europe and for gas storage."
According to analysts, the West feels it must respond to Moscow's use of energy as leverage for control in the region.
"After some years in which Russia was winning in the energy game, the West seems to be gaining the advantage," Less told AFP.
A number of gas transmission projects that will ultimately reduce the region's energy dependence on Russia are underway.
The EU-backed Trans-Adriatic Pipeline (TAP) project to bring Azeri gas via Turkey to Greece, Albania and across the Adriatic to Italy is expected to make its first deliveries in 2020.
In terms of capacity -- 10 billion cubic metres annually -- the 870-kilometre (539-mile) TAP may not appear that important in economic terms.
"It is more a geopolitical project that could enhance, even if only minimally, EU gas security," said Nicolas Mazzucchi, a researcher at the IRIS French think tank.
The West is pushing for a way to reach the Caucasus, and one day perhaps even tap into Caspian or Middle Eastern gas, while circumventing Russian territory, he said.
The EU and the US are willing to extend TAP to create a "gas ring" circling the Balkan region from Albania, through Montenegro and Bosnia, to Croatia.
Along with a planned liquefied natural gas terminal (LNG) on the northern Croatian island of Krk, partly financed by EU, it would create strong competition between the West and Russia.
In May, seven Balkan nations -- Albania, Bosnia, Bulgaria, Croatia, Kosovo, Macedonia and Montenegro -- signed a deal to jointly develop a natural gas pipeline that could diminish their dependence on Russia.
The project is backed by the US development agency USAID.
And the Europeans are backing the Ionian-Adriatic Pipeline (IAP), that would run from Albania, through Montenegro and Bosnia, to Croatia.
For its part, Russia signed a deal with Turkey in October 2016 to build the TurkStream pipeline pumping Russian gas through Turkish waters in the Black Sea towards Europe.
Visiting Turkey this month, Serbian President Aleksandar Vucic said he wanted the pipeline linked to his country.
But experts say the project is highly sensitive in geopolitical terms and technically very demanding. It would require work at depths of up to two kilometres under the sea.
It depends on a whole number of issues, said Igor Dekanic, a professor at the Zagreb Faculty of Mining, Geology and Petroleum Engineering.
These included relations between Turkey, Russia and EU, the migrants issue, Syria, the expert said.
© 2017 AFP