Swiss authorities expect a heavy turnout of voters Sunday as the country decides whether it will join a European free-trade market or cling to its 700-year-old tradition of self-reliance.

In a vote portrayed as one of the most important in Switzerland's history, the referendum will decide whether the country will take part in the 19-nation European Economic Area, starting on Jan. 1.Approval of the plan is widely seen as a step toward the Swiss government's goal of making the nation a full member of the European Community, and away from its history of neutrality and no alliances.

Government leaders made impassioned appeals for approval in the days leading up to the vote, arguing that a rejection would drive away industry.

But opponents said that approval would open the doors to waves of immigrants, cause economic hardships and threaten Switzerland's tradition of grass-roots democracy, which the Swiss trace to the 1291 independence movement of the legendary William Tell.