Montenegro decides Sunday whether to seal the final breakup of the former Yugoslavia's six republics, when it votes in a referendum on severing its remaining links with Serbia.

Shouting "Yugoslavia" at a pre-vote rally, supporters of the pro-Serb Socialist opposition encouraged Montenegrins to vote against independence in Sunday's referendum.

The most recent opinion polls, taken last month, showed about 56 percent in favor of independence.

However, under European Union guidelines, the referendum could be declared invalid, if less than 55 percent of the voters choose independence.

In a television interview, Prime Minister Milo Djukanovic, who favors independence, suggested that an invalid referendum, or a massive no vote, would force his tiny republic to remain in what he considers an uncomfortable arrangement as the junior partner in a loose federation with Serbia. He spoke through an interpreter.

"Because, the current arrangement has proved not to work. Montenegro during the ongoing transition period has been Serbia's hostage," he said.  "The Serbian government was not willing to respect its international engagements for instance. As you know, the Serbian government has refused to collaborate with the international tribunal in The Hague. Serbia and Montenegro have both suffered in their European ambitions. The logical conclusion is that Montenegro has suffered the consequences for something for which it was not responsible."

The federation of Serbia and Montenegro was created three years ago as the successor to what was left of former Yugoslavia, following its violent breakup.

Opponents of independence, say tiny Montenegro, with a population of 620,000, is too small to be viable as an independent state.

Observers and analysts are concerned about the possible consequences of an indecisive result, in which more than half the voters, but less than the needed 55 percent, vote for independence. That would leave Montenegro in a "gray zone," with a majority favoring independence, but not enough to secede.