The flight from Kuala Lumpur to Beijing vanished with 239 passengers and crew. But no wrechage has been found even after three weeks of its disappearance.
The Malaysian Prime Minister Najib Razak announced on March 24 that the plane crashed into ocean, based on detailed analysis of satellite data.
"The accumulation of evidence is that the aircraft has been lost and it has been lost somewhere in the south of the Indian Ocean," Australian PM told reporters at the Perth military base coordinating the search.
"That's the absolutely overwhelming wave of evidence and I think that Prime Minister Najib Razak was perfectly entitled to come to that conclusion, and I think once that conclusion had been arrived at, it was his duty to make that conclusion public."
Australia is coordinating the international hunt for the missing Boeing 777, which involves about 100 personnel searching from onboard surveillance aircraft and 1,000 sailors in ships in or near the search zone.
"This is an extraordinarly difficult exercise. We are searching a vast area of ocean and we are working on quite limited information," Abbott said.
"Nevertheless, the best brains in the world are applying themselves to this task, all of the technological mastery that we have is being applied and brought to bear here. If this mystery is solvable, we will solve it. But I don't want to underestimate just how difficult it is."