Prime Minister John Key this afternoon announced a national memorial service for those who died in the Christchurch earthquake, after today's announcement that the rescue operation was now a recovery operation.

Mr Key said the Government was currently considering issues around the National Memorial Service and more detail would be released as early as Monday.

"At an appropriate time in the coming weeks we will hold a national memorial service in Christchurch to honour those who have died... but today is a day when we as a nation, along with our many friends around the world, mark with a heavy heart and great sadness this moment of unbearable loss for the many families involved.

"I think the country and world recognises the significance of this event - in terms of loss of life, it's likely to be one of New Zealand's most significant.

"All New Zealanders will want to mourn that loss and to grieve for those that have lost their lives and for the significant disruption to our second largest city."

Mr Key indicated the service was likely to be within two or three weeks.

While the memorial service for Pike River was held quite quickly, the situation was more complex for Christchurch partly because of the number of foreign nationals involved, the sheer size of the event and the need to progress the return of loved ones before the service if possible.

Mr Key also said the Government would be extending financial assistance to families of foreign nationals to repatriate the bodies of their loved ones killed in the disaster and also to assist them to come to New Zealand where appropriate.

He said today's announcement the rescue operation in the city had become a recovery meant New Zealand could begin to grieve.

"All of us held onto hope there would be a miracle. Sadly, today's announcements means we must now confront the permanence of that loss.

"As a nation, we were all aware that as the last nine days wore on the chances of those caught up in this terrible tragedy being found alive were decreasing."

He thanked all the New Zealand and overseas Urban Search and Rescue staff who have been sifting through the wreckage of the Christchurch city centre for the past nine days.

"You've all done a tremendous job, the country thanks you for your tireless efforts," he said.

Many stories of courage and bravery would emerge in the coming days, he said.

He said the city's CBD was likely to be closed for at least 6 months.

A Royal Commission of Inquiry into issues around failed buildings was "absolutely an option".

Questioned today on claims help has been slow in getting to the eastern suburbs, Mr Key said: "Given the loss of life in the CBD it's been appropriate to prioritise that".

Earthquake Recovery Minister Gerry Brownlee echoed Mr Key's sentiments and also praised the search and rescue personnel.

"Most jurisdictions reach this point after 72 hours," he said.

"The brave fellas who are out there working on those dangerous sites have given it one hell of a nudge."

Mr Brownlee said the time had come to acknowledge the recovery point had been reached, and some of the overseas teams would return home.

"Some of them will reconsider whether or not they stay here for a longer period of time, others have said they will stay until the job is done," he said.

Governor-General Sir Anand Satyanand said a difficult decision had been made.

"For more than a week we have joined with the families and friends of those missing in hoping for a miracle, that people would be pulled from the rubble alive," he said.

"We must now confront the bitter reality that the possibility that further survivors might be rescued is very small indeed."

Sir Anand said dedicated, highly professional efforts were made to search for the living and recover the remains of those lost.

"The thoughts of all New Zealanders are with the people of Christchurch and all those grieving for the loss of their loved ones."

Search effort now to recover the dead

Earlier this afternoon Civil Defence announced the search for survivors had become a grim effort to recover dead bodies from the rubble of Christchurch's city centre.

National controller John Hamilton said at a press conference there was now no chance of finding anyone alive in the wreckage left by last week's devastating 6.3 magnitude earthquake.

He said Urban Search and Rescue teams had not reached the decision lightly.

"They have put in their very best effort. They have rescued 60 people from the wreckage.

"As time goes on the chances of finding others alive diminishes.

"We now face the reality there is no chance that anyone could have survived this long.

"There becomes a time when the response has to change from rescue to the recovery of bodies and, sadly, we have reached that point," said Mr Hamilton.

He said the possibility - however small - of a miracle survivor being found did exist, but "we need to be realistic and help families come to term with the grim reality."

Mr Hamilton said Civil Defence was meeting with family members of the missing to explain what the transition means.

Jim Stuart-Black, head of Fire Service's Urban Search and Rescue (USAR) teams, said the decision meant buildings were still treated as if they contained people.

"People are handled like family members, with care and respect, as they are removed safely."

The USAR teams will undertake assessments of debris and prioritise for controlled clearing of debris, using machinery. They then deconstruct buildings in a way that allows searching to continue.

Mr Stuart-Black said today's decision had to be made on the facts available to Urban Search and Rescue teams.

Most international disaster responses transition to recovery after 72 hours with no sign of life and it had been eight days since the last survivor of the Christchurch earthquake was found, he said.

However, he said recovery teams were not abandoning all hope.

"There is the occasional miracle. We conduct our operations first of all to allow for that miracle."

Also speaking at this afternoon's press conference, Foreign Minister Murray McCully offered condolences to those who now know for sure they have lost their loved ones.

The New Zealand Government knew their plight and would be offering assistance in the coming weeks, he said.

He acknowledged the up to 100 foreigners from 20 countries that are thought to have been killed in the earthquake.

"The New Zealand Government is very conscious of the position they now find themselves in with today's announcement."

Mr McCully also thanked the hundreds of international workers who helped with the search and rescue operation.

The operation would not have been possible without that their help, he said.

"We have never had any capacity - as no government does - to deal with a disaster on this scale by ourselves."