Australia could pay up to $100 million more for its new fleet of stealth fighters should Canada dump plans to buy F-35, according to a US military estimate.

US Air Force Lieutenant-General Chris Bogdan told a congressional hearing in Washington on Wednesday that a decision by Canada or any country to cancel orders would add about $US1 million ($1.38 million) to the cost of each fighter.

Former prime minister Tony Abbott poses in the cockpit of a replica of the F-35A Lightning II Joint Strike Fighter at Canberra's Fairbairn Airbase in April 2014. Credit:Alex Ellinghausen

The ongoing costs for development of the fighter would also increase.

The extra outlay would be another blow to the troubled F-35 program, which over its nearly two-decade history has been beset by cost overruns and technical difficulties.