The EU Enlargement Commissioner, Johannes Hahn, has summoned Macedonian government and opposition leaders to Brussels on Wednesday for detailed talks on ending the country's crisis.

Hahn is due to meet Macedonian Prime Minister Nikola Gruevski and opposition Social Democrat leader Zoran Zaev in Brussels on Wednesday to discuss an agreement on a transitional period that will lead up to snap elections by next April.

Leaders of the ethnic Albanian bloc, Ali Ahmeti from the junior ruling party, the Democratic Union for Integration, and Menduh Thaci, from the opposition Democratic Party of Albanians, are also expected to attend.

Ahead of the talks, key details remain unanswered. One is whether Gruevski, who has been in power since 2006, will step down as Prime Minister during the transition period and who will be in charge before the early elections take place.

The opposition has demanded the formation of an interim government under whose auspices the electoral roll is checked and electoral flaws are addressed.

“The Macedonian people do not deserve this regime. It must crumble and the first step will be the stepping down of Nikola Gruevski,” Zaev said on Monday in Skopje.

Gruevski has resisted calls to leave office early, and has vowed to win any early elections, however.

He recently told Sitel TV that he accepted early elections only in order “to end the agony in which the opposition has put Macedonia”, adding that “the people will defeat the destructive policies of the opposition” in the elections.

Ahead of the talks, EU spokesperson Maja Kocijancic said all the leaders are expected to participate in and stick to the agreed framework.

The crisis in Macedonia resolves over claims of mass illegal surveillance. The opposition accuses Gruevski of orchestrating the surveillance of over 20,000 people and is demanding that he and his government resign.

Gruevski has insisted that compromising tapes of officials' conversations, which have been released by the opposition Social Democrats since February, were “created” by unnamed foreign intelligence services and given to the opposition to destabilise the country.

The tapes point to election fraud, abuse of the justice system and media and suggest that the government covered up official responsibility for the murder of a young man by a policeman.

As negotiations continue, both sides have also tried to maintain pressure on their opponents on the streets of Macedonia.

The opposition parties, together with civil society groups, set up a protest camp in front of the government headquarters in Skopje on May 17.

The ruling party copied the move and has set up its own counter-camp “for the preservation of democracy” opposite the parliament.