New fighter jets Canada plans to buy will be more than $100 million each — at least $25 million more per plane than government estimates — according to a top U.S. budget watchdog.

Conservative government officials have said 65 new joint strike fighters being built to replace Canada's F-18 jets will cost about $75 million each, about $9 billion with training and an additional $200-$300 million a year in maintenance.

But Mike Sullivan, director of acquisition management at the US General Accountability Office, said he doesn't know where that estimate comes from.

"That's not a number that I am familiar with at all," he said in an interview Tuesday with CBC's Power & Politics with Evan Solomon, cautioning he hasn't seen the methodology behind the numbers.

Sullivan said the estimated cost of the F-35A model that Canada is buying is "in the low 100 millions."

"Probably somewhere between $110-115 million," he said.

Canada buying jets at bottom of cost curve: Tories' Hawn

A prominent Conservative admitted to CBC that the cost of the F-35 fight jets might not be as the government has promised.

Earlier on Power & Politics, Conservative MP Laurie Hawn said Canada is buying the planes at the peak of their production, making them cheaper than the $133 million the U.S. estimates their jets will cost. Hawn also said the $133 million estimate is an average of three models being built, of which the Canadian jet is the cheapest.

"We're buying our planes at the bottom of that [cost] curve," said Hawn, who was parliamentary secretary to Defence Minister Peter MacKay before the election was called.

But when asked whether the cost could change, Hawn replied: "Anything can happen."

Sullivan said that while the last planes off the production line cost less than the first ones, Canada's jets are set to be delivered in 2016, which he viewed as early in the production run.

"That tells me I don't think that's going to be the least expensive buy," he said.