The hunt for underwater signals from missing Flight MH370 is likely to continue for days before a robot submersible is deployed to comb the seabed, according to the Australian search chief.
The detection of sonic pings consistent with those emitted by aircraft black box recorders had raised hopes that a submersible would soon be sent down to the ocean floor.
However, retired Air Chief Marshal Angus Houston said more signals were first needed and acoustic listening would continue until the batteries powering the emissions had expired.
"We need to continue that (search) for several days to the point at which there is absolutely no doubt that the pinger batteries will have expired," Angus Houston said. "Until we stop the pinger search we will not deploy the submersible."
He said that further signals would help to focus the hunt for a possible crash site.
"If we can get more transmissions we can get a better fix on the ocean floor which will enable a much more narrowly focused visual search for wreckage," he said.
Houston said no further transmissions had been detected in the remote search area off western Australia which could help pinpoint where the jet carrying 239 people is believed to have crashed into the Indian Ocean.
"We need another transmission to better refine the area," added Houston.
Up to 11 military planes, three civilian planes and 14 ships are taking part in the unprecedented search 2,268km northwest of Perth, the Joint Agency Coordination Centre said.