By Kole Casule Reuters - Friday, June 13 11:21 am

SKOPJE (Reuters) - Sunday's election re-run in Macedonia's ethnic Albanian areas is a critical test for the Balkan country's European Union accession prospects, officials and diplomats said on Friday.

The first round of elections on June 1 descended into chaos when violent clashes erupted between rival ethnic Albanian parties. One person was shot dead, nine were wounded and voting was stopped in one town after a gun battle.

"This is not a second chance, it is the last chance for Macedonia," a senior western diplomat told Reuters in Skopje on condition of anonymity. "If we again see only violence and intimidation, it could only mean this country is not mature enough to be part of the European family."

Macedonia's ruling conservatives led by Prime Minister Nikola Gruevski won an overwhelming victory, giving him the healthiest majority in parliament in more than a decade, but the result was overshadowed by the election violence.

The European Union and the United States pressured Macedonia to conduct a re-run in areas where violence and intimidation marred the voting, about 6 percent of polling stations.

Although the re-run, covering about 10 percent of the population, will not affect the overall national result, Sunday's vote will give the final verdict on Madeconia's EU and NATO accession chances.

"There is no way around it, voting day must be peaceful. The people should be given a chance to go to the polls without fear. Anything less would be a huge setback that will isolate the country," the diplomat said.

EU Enlargement Commissioner Olli Rehn has stressed free and fair elections are an essential accession criterion.

Macedonian officials said they recognised the importance of a smooth re-run, pledging ministers and politicians will help monitor the vote. They said election irregularities will continue to be prosecuted.

"Sunday will be an important day, both for confirmation of the democratic capacity and for remaining on track for... getting a positive recommendation for opening of accession negotiations in the course of 2008," Macedonian Foreign Minister Antonio Milososki said after meeting EU officials in Brussels.

Macedonia came to the brink of all-out ethnic war in 2001 but the lure of NATO and the EU persuaded Albanian guerrillas to disarm and join politics. The 25-percent Albanian minority is divided between two hostile parties with links to armed groups.

Although the ethnic Albanian rivals, the Democratic Union for Integration (DUI) and Democratic party of the Albanians (DPA) exchanged accusations this week, party officials said their leaders could come out in a televised address to call for peaceful elections in the next two days.

After the re-run, Gruevski will choose one of the rival ethnic Albanian parties as a coalition partner to bolster his majority in the 120-seat parliament.

(Writing by Dina Kyriakidou, editing by Philippa Fletcher)