Bulgaria has refused to sign the Stabilisation and Association Agreement between Montenegro and the European Union because of the spelling of the single currency in the Bulgarian translation of the document.
The announcement was made by Bulgaria's EU Affairs Minister Gergana Grancharova.
The name of the currency in the agreement's body has been written "euro" instead of "evro", as it is transcribed in Cyrillic.
The European Central Bank insists on writing "euro" as one and the same spelling of the word should be used in the translations in all EU official languages.
Interestingly, the spelling of the single currency that figures in Bulgaria's EU accession agreement is "evro". The document ratified by all EU states before the country joined the bloc, says that the euro will be called "evro" in Bulgarian. EU Council legal experts called it a purely technical mistake, which Sofia has refused to "correct".
It is now up to the Portuguese presidency to submit proposals, hoping to get to a solution.
Other countries where the euro is pronounced differently, including Slovenia, which also uses "evro", have tried to obtain a different spelling of the common currency. They all failed - except for Greece.
Bulgaria is in the middle of a battle for keeping the Cyrillic spelling of all the words in the European legal papers. The country is the first to introduce the Cyrillic alphabet as an official one in the block.