Australia will contribute an extra £40.48m (A$79.6m, $63.4m) over the next two years to find missing Malaysia Airlines flight MH370 if the plane is not found in the current official search.
No sign of the plane's wreckage has ever been discovered since it disappeared without trace on 8 March 2014, while the 239 passengers and crew on board are all presumed dead.
Search vessels are trawling the depths of the southern Indian Ocean along the so-called "seventh arc" to find the missing Boeing 777.
The current 60,000sq km search area is set to double due to the boost from Australian government funding.
A budget report said: "The government will provide A$79.6m over two years from 2014-15 to continue the search for Malaysian Airlines flight MH370 should the aircraft not be located in the current search area. This will increase the search area by an additional 60,000sq km to 120,000sq km."
However, it later stated its contribution would be lower if other countries helped to finance the search operation.
In April, Australia's Transport Minister Warren Truss said they were still confident they were searching the right area. He said: "We are confident we have the best search equipment ... if the plane is in the area we will find it."