Serbia’s President Aleksandar Vucic made an unannounced visit to Ukraine on June 11, attending a regional summit in Odesa — his first official trip to the country since taking office over a decade ago.

Vucic, whose visit was disclosed only after his departure from Serbia, participated in the Ukraine-Southeastern Europe Summit in the Black Sea port city, just days after it was hit by a barrage of Russian missile and drone strikes.

The visit risks aggravating already tense relations with Moscow. Earlier this month, Russian intelligence scolded Serbia for supplying weapons to Ukraine, reviving a year-old story that Serbian arms exports were ending up in Kyiv through third-party countries.

In 2024, the Financial Times reported that Serbia had exported around €800mn in ammunition to Ukraine. Vucic did not deny the reports. At the time, Moscow offered only muted responses. The recent outburst, therefore, has sparked rumours about a cooling relationship between the two countries.

Moscow appears increasingly frustrated with its Balkan partner. Though Serbia has refused to impose sanctions on Russia, it has supported several UN resolutions condemning Russia's actions and made statements in support of Ukraine's territorial integrity. At the same time, Serbia has provided millions of dollars in weapons supplies to Kyiv.

Still, Vucic has tried to maintain cordial ties with the Kremlin, even attending Russia’s Victory Day parade in May alongside President Vladimir Putin, despite the EU's warnings. Yet his government’s broader priority appears to be strengthening relations with Western allies.

In recent months, Serbia has hosted several senior Western officials, including European Commission President Ursula von der Leyen, Enlargement Commissioner Marta Kos and UK Foreign Secretary David Lammy. In April, Vucic also met French President Emmanuel Macron in Paris.

Although often pegged as a Russian proxy by the West, Serbia has consistently stated its intention to join the European Union. And on key strategic matters, Vucic’s government leans Westward — committing Serbia’s lithium reserves to Europe and backing Anglo-Australian firm Rio Tinto to develop the mine.

Vucic has to balance his government’s EU aspirations with pro-Russian feeling in Serbia. Vucic faces strong pro-Russian sentiment among large parts of the Serbian public and political right, many of whom oppose closer ties with Ukraine or the West. Unlike his other visits, this trip was not announced in advance, and the public only learned about it after the president had already departed. 

It is not only public opinion that compels Serbia to maintain close ties with Russia. Belgrade is heavily dependent on Russian natural gas, currently paying well below European market prices under a deal with Gazprom. That agreement, extended in May and now set to expire in September, plays a crucial role in Serbia’s cautious diplomacy toward Moscow.

President Vucic's unannounced visit to Ukraine, signalling support for Kyiv and its Western allies, could complicate those ongoing energy talks. Though Serbia is slowly diversifying its energy sources — including recent deals with Azerbaijan — Russian gas remains essential to its energy mix. The current contract, priced around $275 per 1,000 cubic metres, is critical to the country’s energy security.

So far, Russia has tolerated Serbia’s balancing act, including its gestures toward the West and indirect military support for Ukraine. But patience in Moscow may be wearing thin. For the Kremlin, which has few levers of influence left in the Western Balkans, maintaining ties with Serbia — the region’s largest state — is vital. As Russia watcher and bne IntelliNews columnist Mark Galeotti recently told The Spectator: for Russia, it's Serbia (and Republika Srpska) or nothing.