Malaysia said the search area for missing Malaysia Airlines flight MH370 will be doubled in size if no traces of the plane are found within the next few weeks.

Malaysian Transport Minister Liow Tiong Lai said search operations will have covered all the 60,000 square km (23,000 square miles) included in the current search area by the end of May.

"If the aircraft is not found ... we have collectively decided to extend the search to another 60,000 square km within the highest probability area," he said.

Liow and his Australian counterpart Warren Truss said they were nevertheless confident some traces of the Boeing 777 that disappeared with 239 people on board in March last year will be found as searches cover 39% of current search area that remains to be scouted.

"We are confident we are searching in the right area," Truss said. "We are confident we have the best search equipment ... if the plane is in the area we will find it."

The Indian Ocean operation, led by the Joint Agency Coordination Centre and Australian Transport Safety Bureau, has so far cost $90m ($60m).

"Australia and Malaysia have been sharing the cost and we will continue to do that," Truss said. "We are confident we will be able to fund whatever is necessary."

The plane vanished from radar on 8 March last year after veering off its original flight path from Kuala Lumpur to Beijing for reasons still unknown today. Satellite data suggests it crashed along the so-called seventh arc in the Indian Ocean.