Upbeat Abbott updates China

Tony Abbott.

Prime Minister Tony Abbott was to update China's President Xi Jinping on the latest developments in the hunt for missing Malaysia Airlines flight MH370 before he left Beijing last night.

Abbott said he would seek the latest details from the Australian search co-ordinator, retired defence chief Angus Houston.

"What I have tried to do is keep the principal foreign leaders updated whenever there's been significant change," he said in Beijing.

His efforts in selling a trade deal to China appear to have been significantly assisted by Australia's search for MH370. He said there had been appreciation at every level of the Chinese Government. But he played down prospects of an imminent breakthrough.

"While we have a high degree of confidence that the transmissions that we have been picking up are from flight MH370's black box recorder, no one should underestimate the difficulties of the task still ahead of us," he said.

Trying to locate anything 4.5km under the ocean, thousands of kilometres from the Australian mainland, remained a massive task.

Abbott said numerous signals had now been detected, giving a high degree of confidence they were coming from the aircraft's black boxes. "Given that the signal from the black box is rapidly fading, what we are now doing is trying to get as many detections as we can so that we can narrow the search area down to as small an area as possible."

Submersibles would then be used to conduct a sonar search of the seabed.

- AAP