"The decentralisation is a cornerstone of the Ohrid accord and an essential element to ensure the integration of the former Yugoslav republic of Macedonia into euro-Atlantic institutions," Rizzo told a press conference in Sofia on security in the Balkans.

The referendum in Macedonia has been organised by opposition parties opposing an EU-backed law which changes municipal boundaries to empower the ethnic Albanian minority.

The law sparked riots when it was passed in early August and is widely seen among the Macedonian majority as a step toward federalisation along ethnic lines.

It has strong backing in Brussels though, where it is seen as the last step in the Ohrid peace accords which ended a six-month uprising by ethnic Albanian guerrillas in 2001.

British Minister for Europe Denis MacShane earlier this week called on Macedonians to boycott the vote, saying an expected 'No' vote would be anti-Europe.

Rizzo urged Macedonians not to sink the law when they go to the polls, saying it was "particularly important for ... Macedonia's future to ensure this decentralisation."

Rizzo, the defense and interior ministers of the Balkan states, and EU representatives are holding a two-day meeting in the Bulgarian capital.

The European Union's special representative for Macedonia, Michael Sahlin, told AFP that if Macedonians were to vote against the law next Sunday, it would delay the country's accession to both the EU and NATO.

"If it is successuful, it means that the country will find itself in a very difficult political, constitutional and may be also security related situation. It would be a delay in any case to the accession to EU and NATO."

Sahlin said however that he believed less than the required fifty percent of the electorate would turn out, making the outcome of the vote invalid.

"I think still that the probability is that the referendum will not be valid or successful meaning that not more than 50 percent will participate and say yes to the questions as asked," he said.

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