The European Union has warned Bern that bilateral accords with Switzerland could be torn up if the Swiss do not approve extending a free movement treaty to Romania and Bulgaria.
In an interview on Saturday with the French-language newspapers, 24 Heures and Tribune de Genève, the EU ambassador, Michael Reiterer, reminded the Swiss of the "guillotine" clause in the accords.
"There is no room for speculation or reason to play for time," Reiterer said.
However, the EU ambassador to Bern said he was confident the Swiss would approve the extension of the free movement of people treaty to the two newest EU members when it came to a nationwide vote on February 8.
He said this was despite the numerous "untruths" being spread by anti-EU campaigners including the argument that Switzerland would be flooded with immigrants.
Reiterer added that businesses would be the main beneficiaries although there would be fewer openings in the Swiss job market for qualified foreign staff due to the looming recession.
There is also no evidence that the implementation of the treaty leads to an increase in crime. The opposite is true, he said, since security will improve with Switzerland's entry into the Schengen zone on Friday.