Australian Prime Minister Tony Abbott admitted that it is highly unlikely to find any aircraft debris from the missing Malaysian Airlines (MAS) flight MH370 on the ocean surface and that the search for the aircraft will enter a new phase.

Abbott also admitted that none of their search efforts, whether in the air, on the surface, or undersea, have yet to stumble upon any wreckage.

"I am now required to say to you that it is highly unlikely at this stage that we will find any aircraft debris on the ocean surface," he said at a press conference in Perth.

Abbott explained that the new search will focus on searching the ocean floor over a much larger area.

"What we are going to do is to enter a new phase of search focusing under the sea. The Bluefin-21 submersible will continue in operation.

"We are looking to intensify underwater search involving different technology in particular using specialised side scan sonar equipment to scan the seabed for evidence of wreckage," he said.

Abbott added that the Australian government and the Malaysian government will engage one or more commercial companies to undertake this work.

"This work would be done under contract to the Australian government.

"It could take us some weeks to put in place this new contractual arrangements for an intensified undersea search," he said.

Abbott said that the search and rescue team have now searched close to 400 square kilometres undersea.

"Essentially, what we are looking to do is to conduct as thorough an undersea search as humanly possibly, if necessary of the entire probable impact zone which is roughly 700 kilometres by 80 kilometres," he said.

Abbott added that during the period to put in place new contractual arrangements, there will be a dedicated number of vessels from Australia, Malaysia and China that will continue Maritime operations to maintain continuity and momentum.