Australia's Prime Minister Tony Abbott has said that the hunt for a missing Malaysia Airlines plane will be expanded to include a massive swath of ocean floor that may take eight months to search thoroughly.
The US Navy's Bluefin 21 robotic submarine has spent weeks scouring the initial search area for Flight MH370 in the southern Indian Ocean, but has found no trace of the aircraft.
Abbot said that officials were now looking to bring in new equipment that can search a larger patch of seabed for the plane, the AP news agency reported.
"It is highly unlikely at this stage that we will find any aircraft debris on the ocean surface," the Australian leader told reporters at a news conference in Canberra, the capital.
"By this stage, 52 days into the search, most material would have become waterlogged and sunk."
Radar and satellite data suggests the plane carrying 239 passengers and crew veered far off course on March 8 for unknown reasons during a flight from Kuala Lumpur to Beijing.
Analysis indicates it would have run out of fuel in the remote section of ocean where the search is focused.'
'Crippling cloud of uncertainty'
Bluefin 21 has been creating three-dimensional sonar maps of the search area for nearly two weeks after signals consistent with black boxes were heard on April 8.
The initial search zone was about 400 square kilometres but teams will now begin searching the plane's entire probable impact zone, an area 700km long and 80km wide, Abbot said.
The head of the search effort, Angus Houston, said that weather and technical issues could cause the search to drag on well beyond the eight month estimate.
Australian officials will ask private companies to bring in additional sonar equipment to help the search effort, at an estimated cost of $60m.
It could take officials several weeks to organise contracts for the new equipment and the Bluefin will continue to scour the seabed in the meantime, the prime minister said.
Each country involved in the search has so far been bearing its own costs, but Abbot said his country would seek contributions from other nations to help pay for the new equipment.
Two weeks ago, Abbott said officials were "very confident" that a series of underwater signals picked up by sound-detecting equipment came from Flight 370's black boxes.
On Monday, he maintained that he still had a "considerable degree of confidence" but said it was possible that the signals were another dead end.
Abbott also acknowledged it was possible that no debris from the plane would ever be found but said Australia would do everything it "reasonably" can to find the plane.
"We do not want this crippling cloud of uncertainty to hang over these families and the wider travelling public," he said.