British Prime Minister Theresa May and French President Emmanuel Macron are set to commemorate their countries shared sacrifice in the First World War on Friday and discuss the future of their post-Brexit relationship.
The memorial commemorates 72,337 missing British and South African servicemen who died between 1915 and 1918 in a series of battles along the Somme river and who have no known grave.
May was to start the day with a visit to St Symphorien Military Cemetery in Mons, in Belgium, where she and Belgian Prime Minister Charles Michel were to lay a wreath at the graves of the first and last soldiers killed on the Western Front.
"A century ago British forces fought side by side with our allies in Europe on the Western Front. Today in France and Belgium we reflect on our shared history, but also look ahead to our shared future, built on peace, prosperity and friendship," May said in a statement.
Following a reception with British and Belgian serving armed forces in Mons, May will travel to France where she will meet Macron in Albert, a town in the heart of the Somme region which suffered significant bombardment during the First World War.
The leaders will hold a working lunch, where Brexit is expected to be top of the agenda, before laying a wreath at the Thiepval Memorial.
The wreath, made for the occasion, will combine poppies and le bleuet, the two national emblems of remembrance for Britain and France.
France has taken a hard line in Brexit negotiations, with President Emmanuel Macron insistent that Britain should not be allowed to negotiate advantages for itself as it withdraws from the European Union.
Negotiators have been racing the clock to try to agree the outlines of an agreement to settle Britain's exit that could be approved at a summit of EU leaders in Brussels this month.
But hopes of meeting that deadline are fading.
Britain's foreign minister played down the prospect of an imminent deal on Thursday and called for greater efforts to be made in the negotiations to "understand the other's perspective."
On Saturday, May is to attend the Royal British Legion Festival of Remembrance at the Royal Albert Hall in London.
On Remembrance Sunday, she will lay a wreath at the Cenotaph in London and attend the national service to mark the Centenary of the Armistice at Westminster Abbey.