The Queen, the Duke and Duchess of Cambridge and The Duke and Duchess of Sussex all sent their condolences to the victims of the attack.
In a joint statement from Prince William, Prince Harry, The Duchess of Cambridge and the Duchess of Sussex they said their hearts went out to the families and friends of the people who lost their lives.
"We have all been fortunate to spend time in Christchurch and have felt the warm, open-hearted and generous spirit that is core to its remarkable people.
"No person should ever have to fear attending a sacred place of worship."
Many global leaders of the Muslim Community were also likely to be in attendance making it a huge security and logistical operation.
An Australian delegation was also likely.
On Monday, Ardern said it was important to give the families affected by the shooting the opportunity to grieve but anticipated making an announcement about the event soon.
"What we want to ensure is that we allow the time and the space for the families to be able to bury their loved ones; keeping in mind that some have not yet received their loved ones," she said.