The 3.2GW plant is predicted to produce electricity for around six million British homes.
In a meeting with French President Emmanuel Macron at the European Political Community summit in Prague, Liz Truss confirmed that both countries are committed to fully supporting the new nuclear power station at Sizewell C.
Both leaders pledged to take all necessary steps to finalise investment decisions within the next month.
It has been reported that the agreement between the two parties could come in the next two weeks and see each take a 50% share in the company responsible for developing the project.
Prime Minister Liz Truss said: “The UK will continue to work with our allies to deliver on the British people’s priorities, including ending our reliance on authoritarian regimes for energy and reducing costs for families, tackling people-smuggling gangs and standing up to tyrants.”