Serbia has been warned that its hopes of European ascension could be harmed if its president travels to Moscow next month for Vladimir Putin’s Victory Day parade. According to Russian state media, Aleksandar Vucic is one of the dignitaries invited to the celebration on 9 May, something that would “not be taken lightly on the European side.”

European officials have warned that any visit could hamper the country’s hopes of joining the bloc, with it seen as a breach of its membership criteria. Jonatan Vseviov, the secretary-general of Estonia’s ministry of foreign affairs said: “We need to ensure that they understand that certain decisions come at a cost. The consequence is them not joining the European Union.”

He added: “Russians have been working hard to get people to attend. For us this will be an important litmus test. Basically what we look at is whether or not they are on our side or playing on the other team.”

Serbia commenced its plan to join the bloc in 2009 and was made a candidate for membership in 2012.

Despite this, it has a long history of maintaining a relationship with both Russia and Europe, with Vucic welcoming Putin to Belgrade in 2019.

Belgrade has refused to adopt sanctions against Russia taken by most EU countries, something that is already likely to jeopardise its chances of being admitted into the bloc.

Russia is able to exert significant influence on Serbia and is the owner of the country’s only oil refiner, contributing to Belgrade being reliant on Moscow economically.

Kaja Kallas, the EU’s top foreign diplomat said that the potential attendance of leaders of EU nations or prospective members had been discussed at a meeting on Monday.

She told reporters: “What was also discussed very clearly, and said by different member states, is that any participation in the May 9 parades or celebrations in Moscow will not be taken lightly on the European side, considering that Russia is really waging a full-scale war in Europe.”

Ms Kallas has warned EU leaders not to attend Putin’s Victory Day Ceremony, with some known to be sympathetic to Russia.

Hungary’s Victor Orban who has frustrated EU measures against Russia in the past and is viewed as Putin’s strongest ally in the bloc, has announced that he will not attend.

Last year, Slovakia’s new prime minister Robert Fico said he would attend but it remains to be seen whether or not that is still the case.

Ms Kallas said: “I’ve also called all the member states but also representatives of the institutions to visit Kyiv as much as possible to show really our solidarity and that we are with Ukraine.”