Swiss voters go to the polls to decide if their country should join the United Nations.
The government is urging a "yes" vote in the referendum, saying that staying out of the world body denies Switzerland a full role in world affairs and jeopardizes its position as an international monitor.
Opponents say U.N. membership would force Switzerland to abandon its cherished neutrality, which it has held since the early 19th century, and undermine the country's sovereignty by forcing it to submit to the will of the U.N. Security Council.
Swiss voters rejected a similar referendum in 1986 by a three-to-one margin. Last March, they overwhelmingly voted down a proposal to enter into membership talks with the European Union.
Switzerland hosts the European headquarters of the United Nations and eight of its agencies. The country is one of the largest contributors to the U.N. budget, but has only observer status at the 189-member General Assembly in New York.
Under the Swiss constitution, today's referendum has to carry a majority nationwide and win more than half the votes in most of the country's 23 cantons.
Political observers say the referendum is likely to win popular approval, but the cantonal vote may go either way.