Supporters of closer ties with the European Union have called on voters to approve a people's initiative to begin immediate talks with Brussels on EU membership. The issue will come to a nationwide vote in March.
Members of the initiative committee said in Bern on Tuesday that Switzerland was at a crossroads.
"We have to decide whether we want to take part in building the future of Europe, or whether we remain isolated," said the committee's president, Marc Suter.
Another speaker said: "It is no use delaying the question any more, because the longer we wait the higher the political price Switzerland has to pay for EU membership."
However, the committee recognised that its chances of winning on March 4 are slim. It hopes to score a symbolic victory by convincing a majority of voters and at least seven of the 26 cantons to vote in favour.
To pass, the initiative must be accepted by both a majority of voters and a majority of cantons.
The government and parliament have come out against the initiative, saying it is too early to seek membership talks with Brussels.
Last year, voters approved a series of bilateral accords with the EU, but ratification of the treaties is still pending in most EU member countries.
The pro-Europe initiative was launched in 1995 and is supported mainly by centre-left parties and trade unions. But most centre-right parties, which have a majority in parliament, and the cabinet are opposed.
swissinfo with agencies