The agreement marks another milestone in efforts to launch direct train services between London and key Swiss cities including Zurich, Basel and Geneva.
Eurostar, which is majority-owned by SNCF Voyageurs, announced last year that it was exploring new routes from the UK to both Switzerland and Germany as demand for international rail travel continues to grow.
The companies said the new agreement represents “an important milestone” in the long-term planning process for a direct connection between Britain and Switzerland.
In a joint statement, Eurostar, SNCF Voyageurs and SBB said: "The demand for international rail travel is high, and Eurostar, SBB and SNCF Voyageurs see significant potential for connecting London to Switzerland.
"This is because London is the number one flight destination from Switzerland, and at the same time, there is strong customer demand for a direct rail connection to the United Kingdom."
Studies carried out by the operators found potential routes between London and Switzerland could meet growing demand from both leisure and business travellers.
Journey times are expected to range between five and six hours depending on the destination.
The rail operators will now begin analysing possible timetables and operational plans for the future service, which they hope can launch “as soon as possible”.
However, several hurdles remain before the route can become reality.
The project still requires major infrastructure development as well as intergovernmental agreements between the countries involved.
Because of this, the earliest possible launch date is currently expected to fall “sometime in the course of the 2030s”.
The announcement also follows an agreement between SNCF and SBB earlier this year to extend their rail partnership through to 2032.
The proposed route would offer travellers an alternative to short-haul flights between the UK and Switzerland, with rail operators increasingly focusing on international expansion as passengers seek more sustainable travel options across Europe.
