Malaysia warned Thursday that the search for flight MH370's wreckage in the vast depths of the Indian Ocean will be "huge", the latest sobering assessment by authorities involved in the challenging effort.
"When we look at salvaging (wreckage) at a depth of 4.5 kilometres (2.8 miles), no military out there has the capacity to do it," Transport and Defence Minister Hishammuddin Hussein told reporters in Kuala Lumpur.
"We have to look at contractors, and the cost of that will be huge."
The search in a remote stretch of ocean far off western Australia was enlivened in the past two weeks by the detection of signals believed to be from the Malaysia Airlines plane's flight data recorders on the seabed.
But the transmissions have gone silent before they could be pinpointed, raising the spectre of a costly and extensive search of a large swathe of ocean floor at extreme depths.
Prime Minister Tony Abbott of Australia, which is leading the multi-national search, had earlier warned in an interview published Thursday that an autonomous US Navy sonar device that began scanning the seabed for wreckage on Monday would be given one more week.
If nothing is found, authorities would reassess how next to proceed in the unprecedented mission to find the plane, Abbott said in the Wall Street Journal.
The Bluefin-21 completed its first full scanning mission early Thursday.
An initial attempt was aborted when the sub hit its maximum depth at 4.5 kilometres. A second was cut short by unspecified "technical" troubles.
Hishammuddin said he agreed with Abbott, saying "there will come a time when we need to regroup and reconsider".
"But in any event, the search will always continue. It's just a matter of approach," said Hishammuddin, who did not specify what any alternative approach would be.
Australia's search chief Angus Houston said earlier this week that authorities already were looking at possible alternative methods, including undersea devices that can go deeper than the Bluefin-21, but he also gave no specifics.
The Beijing-bound Malaysia Airlines flight with 239 people aboard inexplicably veered off its Kuala Lumpur-Beijing course on March 8, and is believed to have crashed in the Indian Ocean.