The best leads in the underwater search for Malaysia Airlines flight 370 will be exhausted in about a week, Prime Minister Tony Abbott says.

In an interview with the Wall Street Journal on Wednesday, Mr Abbott said if the Bluefin-21 underwater drone scanning the Indian Ocean's seabed in the search area fails to locate wreckage, there would need to be a rethink.

A Bluefin-21 is craned over the side of Australian Navy vessel Ocean Shield in the search for missing Malaysia Airlines Flight MH370. Credit:Getty Images

"We believe that search will be completed within a week or so," Mr Abbott said.

"If we don't find wreckage, we stop, we regroup, we reconsider."