The European Commission terminated the talks on cross-border electricity trade with Switzerland, following the country's referendum on limiting immigration.
"The EU cannot continue the negotiations without further clarity on the matter", said EC spokesperson Sabine Berger.
"No technical negotiations on the electricity agreement between Switzerland and the EU are foreseen for the moment," she added.
Separately, senior European officials said Switzerland could lose its privileged access to the European single market in general following the narrow vote in the referendum on Sunday.
Last weekend the Swiss citizens approved by a narrow margin the reintroduction of quotas on foreign workers, including from EU member states.