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.