Australia has agreed to be an "accredited representative" of Malaysia in the investigation into missing Malaysian Airlines Flight MH370, a development that could lead to the lengthy probe into the jet's disappearance being based there.
The announcement was made by Malaysia's Prime Minister Najib Razak on his visit to Perth and came as the search zone was "further refined" and shifted north as aircraft, ships and a nuclear submarine continued the hunt for remnants of the passenger plane.
As revealed by Fairfax Media, a group of nations have been pressing Malaysia to allow the investigation into MH370 to be based in Australia amid concerns about the chaotic handling in Kuala Lumpur of its disappearance.
While Malaysia will formally head the investigation as required by international convention, Mr Najib told media on Thursday that Australia was now "an accredited representative".
Australia is understood to be one of several nations deemed as an "accredited representative" but it is a step towards shifting the investigation's base here.
Further negotiations will need to take place before a final decision is made on the change, a well-informed source said and Malaysia .
Mr Najib suggested as much when he said: "We will continue to work closely with the Australian government to draw up a comprehensive agreement on the search."
The Malaysian Prime Minister would not take media questions.
"At this difficult time, Australia has proven an invaluable friend. The Australian authorities, like so many others, have offered their assistance without hesitation or delay."
In a joint statement alongside Australian Prime Minister Tony Abbott, Mr Najib paid tribute to all those involved in the search for Flight MH370.
"Differences have been set aside as 26 nations have united behind a common cause, the disappearance of MH370 is without precedent," Mr Najib said.
"The search area is vast and the conditions are not easy, but a new refined area of search has given us new hope and I believe the courage of the crews is more than equal to the task."
That new search area is some 200 kilometres north of the search area identified by authorities last week and is more than 200,000 square kilometres in size.
On Thursday, up to eight planes and nine ships were involved the search about 1680 kilometres west north-west of Perth.
The Joint Agency Coordination Centre described conditions as "fair", with visibility at about 10km.
Mr Abbott described the search as "the most difficult in human history".
"I can assure people that the best brains in the world are working on this, and everyday working on the basis of just small pieces of information. We are putting the jigsaw together and every day we have a higher degree of confidence that we know more about what happened to this ill-fated flight."
Mr Abbott also directly addressed the families.
"Please be patient, I know this is an extraordinary difficult, indeed devastating, time for you but we will not let you down.
"We cannot be certain of ultimate success in the search for MH370 but we can be certain that we will spare no effort, that we will not rest until we have done everything we humanly can."
On the multinational investigation, Mr Abbott said it should inspire confidence, noting nations that don't ordinarily co-operate closely were doing so in this instance.
"I say to anyone who might be inclined to pessimism about international peace and harmony, this is an antidote to pessimism. This is an example of how the countries of the world can work together. This is one of those times when we are all citizens of one world."
- Sydney Morning Herald