The EU's credibility is at stake after European foreign ministers failed to agree on sanctions against Belarus, the bloc's top diplomat said on Monday.
Josep Borrell, the EU's foreign policy chief, said Cyprus had prevented them from reaching unanimity on the issue.
Brussels has rejected the official results of the August 9 Belarusian presidential elections, which credited long-time incumbent Alexander Lukashenko with over 80% of the vote. Lukashenko's critics say the election was rigged in his favour.
The EU has also condemned the subsequent violence unleashed against protesters and warned that it would "swiftly" impose sanctions on the people responsible for the rigging of the ballot and the repression.
Borrell said earlier this month that European foreign affairs ministers were expected to draw up restrictive measures against Belarusian officials on September 21.
But Borrell told reporters on Monday after the meeting that "although there is a clear will to adopt those sanctions, it is not possible to do that today because the required unanimity was not reached."
"Cyprus is missing to give us unanimity," he went on.
Cyprus blocked the decision on Belarus, denying it as veto unless similar measures are adopted against Turkey for its illegal drilling in Cyprus' ´Exclusive Economic Zone.
There is no veto, as a compromise is still reachable as Nikos Christodoulides Minister for Foreign Affairs of Cyprus told Euronews.
"The Republic of Cyprus supports sanctions and doesn´'t put a veto on the table regarding Belarus. But there was a decision that the proposals over sanctions on Belarus and the proposals that Cypriots submitted over Turkey would move forward in parallel so that they would be immediately adopted."
EU leaders are now expected to try to break the deadlock when they meet in Brussels on Thursday.
Latvian foreign minister Edgars Rinkevics described Nicosia's position as "hostage-taking" and said that it "sends a wrong signal to Belarusians, our societies and the whole world".
Borrell, for his part, said: "I will do whatever I can in order for the next Foreign Affairs Council sanctions against Belarus be adopted."
"It is becoming a personal commitment because I understand clearly that (on) it depends very much the credibility of the European Union and the forging of a foreign affairs policy, a common foreign affairs policy, our capacity of sanctioning Lukashenko. If we are not able to do that then I understand perfectly that our credibility is at stake," he added.
Prior to the meeting, Belarusian opposition candidate Sviatlana Tsikhanouskaya appealed to members of the Foreign Affairs Council to "be more brave" and call for fresh election in the eastern European country.
"We did a lot to manage with this situation by ourselves, with only the strength of the Belarusian people, but now I understand that we need exterior help," she said.
She added that "sanctions are very important in our fight" to pressure the government and urged reluctant member states "just to be more brave".