Relatives of those killed in the Omagh bombing are set to gather to remember their loved ones 20 years on.
An inter-denominational service will take place at the memorial garden in the Co Tyrone town at 3pm on Sunday.
Bereaved families expressed disappointment last week after Northern Ireland Secretary of State Karen Bradley and Taoiseach Leo Varadkar turned down invitations to the event.
The UK government will be represented by a senior Northern Ireland Office official, while Enterprise Minister Heather Humphreys will attend on behalf of the Republic of Ireland.
A car bomb ripped through Omagh on August 15 1998 killing 29 people, including a woman who was pregnant with twins, and leaving more than 200 others injured.
The victims came from Northern Ireland, the Republic of Ireland, England and Spain.
The atrocity was claimed by a republican splinter group which called itself the Real IRA.
At Sunday's memorial event, the Omagh Community Youth Choir will perform a piece of music composed for the event by its musical director Daryl Simpson.
The choir includes Cara McGillion, 17 , the daughter of Donna Marie and Garry who were left seriously injured in the attack.
Local singer Leslie Matthews and St Eugene's band will also perform.
On Wednesday, a public reflective event will take place at 2.55pm to mark the moment the bomb exploded.
A bell will be rung 32 times to reflect the 31 lives lost, with an additional ring to remember all those who have lost and continue to lose their lives through such atrocities across the world.
The bell will stop ringing at precisely 3.10pm to mark the exact moment of the explosion.