Swiss President Doris Leuthard has called for a referendum to clarify the country’s future relationship with the European Union, of which it is not a member.

Talks on securing a new “framework” treaty to govern the Swiss-EU relationship have been underway for some time.

As reported by the Reuters news agency, relations soured this month when the EU granted Swiss stock exchanges only limited access to the bloc, prompting Swiss threats of retaliation for what it called discrimination.

“The bilateral path is important,” Leuthard told Swiss newspapers Sonntags Blick. ”We therefore have to clarify our relationship with Europe. We have to know in which direction to go. Therefore a fundamental referendum would be helpful.”

According to Reuters, talks on a an all-encompassing agreement made headway last month after Switzerland agreed to increase its contribution to the EU’s budget.

Such a deal would ensure Switzerland adopts relevant EU laws in return for enhanced access to the bloc’s single market, crucial for Swiss exports, according to Reuters.

But a deal would be opposed by the anti-EU Swiss People’s Party (SVP), currently the biggest group in parliament.