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.

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.

Canada's prime minister-elect Justin Trudeau has pledged to withdraw from the nine-nation deal including Australia and the US to share the costs of developing the fighter jet.

Former prime minister Tony Abbott had committed Australia to buying a total fleet of 72 Joint Strike Fighters, as the F-35 is known.

Defence officials told a senate inquiry in Canberra this week the budget for the F-35 was $17 billion - but the purchase and running costs has been put at as high as $24 billion.

Canada's outgoing Conservative government had originally planned to buy at least 65 of the jets, but Mr Trudeau has promised to seek a cheaper option.

Norway, the Netherlands, Japan and Israel are among the partners in the F-35 program.

General Bogdan, the head of the F-35 program, said he was speaking in general terms about the cost implications and it was not appropriate to comment on Mr Trudeau's election.

A spokesman for Lockheed Martin, the defence company developing the fighter, said Canada was a "valued partner" and there not been any formal notification from the government about their status in the F-35 program.

Doubts around the F-35 have centred on its ability to measure up to the latest Chinese and Russian jets, along with claims Chinese hackers stole sensitive design plans.

Australia has already purchased two F-35s at more than $126 million each and intends to gradually increase the total number to 72 jets by 2023.

Should $US1 million be added to the price tag for the next 70, the cost in today's exchange rate would be an additional $97 million.

Officials told a Canberra Senate hearing on Wednesday evening - ahead of General Bogdan's comments - that the Canadian decision was unlikely to have cost implications for Australia.

RAAF Air Vice-Marshal Chris Deeble also said Australia expected the cost for each aircraft to drop to around $90 million when the final nine jets were purchased in 2023.

He said the stealth jets were in a testing process.

"But it is on track. This is a very complex program, however, and there will always be issues that you will strike," Air Vice-Marshal Deeble said.

The first F-35s are expected to enter service in 2020.

Further comment is being sought from the Defence department.

with Reuters