French President Francois Hollande and German Chancellor Angela Merkel are to mark the 100th anniversary of the battle of Verdun, the longest battle during World War One.
Hundreds of thousands of French and German soldiers died during 10 months of fighting in north-eastern France.
France eventually emerged victorious.
Verdun is seen as a symbol of Franco-German reconciliation, and Mr Hollande and Ms Merkel are expected to renew a call for European unity.
Speaking ahead of Sunday’s commemorations, Ms Merkel said: “To be invited to these commemorations shows the extent to which relations between France and Germany are good today.”
“Europe faces difficult tasks, there is no doubt about that,” she said, in what was seen as a reference to the EU’s continuing economic problems, its attempts to deal with a huge influx of migrants and sharp differences among individual states on the future of the 28-member bloc.
But Ms Merkel stressed that “Europe has also done and achieved many things”.