The Swiss parliament's upper chamber on May 27 supported a motion that would toughen measures to expel spies.
The proposal, which has already been supported by the parliament's lower chamber, is seen as a means to curb Russian intelligence activities in the country ahead of the June peace summit for Ukraine.
The upper chamber – the Council of States – passed the motion with 32 voting in favor, nine against, and two abstentions.
"Foreign states should feel Switzerland is reacting to violations of its security and defending itself," said Swiss President Viola Amherd in an address to the parliament.
The president stressed that the motion would not lead to automatic decision-making.
Bern has previously said that Russia operates spies inside Switzerland disguised as diplomats. Similar accusations have been made by governments across Europe, often leading to expulsions.
Lawmaker Franziska Roth, one of the lawmakers backing the proposal, said that "Switzerland, as the seat of international organizations and as a state in the heart of Europe, is an attractive location for intelligence services."
The peace summit will take place on June 15-16 in the Burgenstock resort above Lake Lucerne, and some 90 countries have already confirmed their attendance. Russia has not been invited to participate at this stage, and Kyiv warned that Moscow will seek to disrupt the conference.
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