David Cameron and Enda Kenny will visit First World War graves and memorials on the former Western Front in the latest step towards deepening British-Irish relations.
The British prime minister and Irish Taoiseach will pay their respects to those who gave their lives in the First World War at several sites across Flanders in Belgium.
Mr Cameron will use the visit to announce new funding to help conserve, repair and protect First World War memorials and graves across the UK and overseas where British and Commonwealth servicemen and women are buried.
The British prime minister said: "Next year's centenary of the start of the First World War will be a time for the whole nation to reflect on the events that saw so many young people of that generation make the ultimate sacrifice.
"Nearly all of us in Britain have some family connection with that conflict, and it is the many millions of small, personal stories that resonate as loudly for us as the big, world-changing battles and campaigns.
"As part of that, it is absolutely right that we help communities up and down the country to ensure that their local war memorials are a fitting tribute to the fallen and increase people's understanding of what happened.
"We simply should not tolerate damaged war graves in our country. Our memorials and cemeteries must be places of respect and education. This funding will help make it happen, and I am proud to be able to announce it today."
Announcing the joint visit last month, Mr Kenny said that following the visit of Britain's Queen Elizabeth to Dublin in 2011, he and Mr Cameron had been keen to mark the sacrifice of those killed, missing or injured on the battlefield.
He said: "When Queen Elizabeth visited the Republic, the first visit by a reigning monarch in a hundred years, she closed a circle of history and recognised in so many deep ways the story of 50,000 soldiers from the Republic who fought with the Allies in World War One."
The leaders will visit the Irish Peace Park at Messines, a memorial to the 50,000 Irish war dead, before travelling to the grave of William Redmond, nationalist politician and Member of Parliament in the Irish Parliamentary party.
Redmond was commissioned as a captain in the Royal Irish Regiment, with whom he served 33 years, and went to France with the 16th (Irish) Division, in the winter of 1915/16 .
In response to the execution of the leaders of the 1916 Easter Rising, Redmond requested that in the event of his death his grave be located outside the walls of the British military cemetery at Locre. This wish was granted.
Afterwards, they will visit the village of Wytschaete, where the 16th (Dublin) and 36th (Ulster) divisions advanced together in the bloody 1917 Messines Ridge offensive.
Mr Cameron and Mr Kenny will then travel to the Menin Gate Memorial, dedicated to British and Commonwealth soldiers whose graves are unknown, where they will be joined by Belgian prime minister Elio Di Rupo.
The tour will finish at Tyne Cot Cemetery, the largest cemetery for Commonwealth forces in the world.
The extra cash announced by Mr Cameron is funded by the Libor fines and spread over the four years of the First World War centenary.
It will also fund new educational materials including downloadable guides to help explain the importance of sites and to honour the sacrifice of those buried or commemorated there.
The British Department for Culture, Media and Sport (DCMS) will talk to organisations including the Commonwealth War Graves Commission, War Memorials Trust, English Heritage, the Wolfson Foundation, about how to make sure communities can access the money, which will be available from next year as grants to local communities who apply and whose application qualifies.
Frances Moreton, director of War Memorials Trust, said: "We are delighted to hear about this additional funding and look forward to working closely with DCMS, English Heritage and others to ensure that war memorials across the UK are repaired and conserved through the centenary."
Alan Pateman-Jones, director-general of the Commonwealth War Graves Commission, said that it was important to ensure future generations understood both the reasons for and the circumstances surrounding the sacrifices made.
"Such generous financial support will enable the commission to better engage and explain its worldwide task and, through this, ensure ongoing commemoration," he added.
Simon Thurley, chief executive of English Heritage, said that the organisation would grant listed status to 500 war memorials each year as it remembered the First World War.
He added: "These memorials represent the greatest wave of commemoration ever seen in this country: listing will ensure that they receive proper attention.
"They stand at the hearts of communities across the land and we want to help ensure that these highly poignant reminders are kept in a condition befitting their importance."