The U.S. deputy secretary of defence says he'd like the Canadian government to make up its mind, one way or the other, whether it will replace its aging CF-18 fleet with Lockheed Martin's F-35 fighter jets.

"Because Canada has been a partner in the F-35 program, if they withdraw — I think it's 65 airplanes — the price for all the other members in the coalition goes up slightly," said Robert Work, in an interview with Rosemary Barton, host of CBC News Network's Power & Politics.

The Conservative government had planned to acquire 65 F-35 stealth fighter jets for the Royal Canadian Air Force, but the procurement process was put on hold after the auditor general accused the government of fudging the project's costs and not doing sufficient research. During the last election Justin Trudeau announced his party would scrap the Conservatives' troubled F-35 fighter jet program. (Daniel Hughes/U.S. Air Force/Reuters) F-35

One of the new Liberal government's main campaign pledges was to buy a less-expensive aircraft and plow the savings into the navy.

However, since taking office, Canada's Minister of Public Services and Procurement Judy Foote has said Lockheed Martin's F-35 fighter jets may still be in the mix to replace Canada's CF-18s.

Most costly weapons program in U.S. history

"It's important for Canada to make the decision on the aircraft that they need for their national interest, and then the United States and Canada can work it out," said Work.

Work said he doesn't think the Canadian government is dragging its feet, but the U.S. is watching closely.

"I work in the Pentagon, so I measure time different ways than other people, so I don't believe it's been long. These are very important political decisions and defence decisions for Canada to make, and we're not trying to pressure them in any way," said Work in an interview at the Pentagon.

"We'd like to know, we're anxious to know, where exactly will you go so we can start to plan together. But these types of decisions are made in due course and we're looking forward to the final decision."

The F-35 program was developed by Lockheed Martin to promote a common system between allied partners including the U.S, Britain, the Netherlands, Italy, Turkey, Denmark, Norway and Australia.

In 2010, the U.S. committed to buying 2,443 aircraft, making it the most costly weapons program in U.S. military history. It's been beset with delays and technical bugs, many of which are related to the development of the fighter's software​.

In 2013, Orlando Carvalho, executive vice-president of aeronautics at Lockheed Martin, warned that Canada's aerospace industry would likely fall out of favour if Canada withdrew its intentions to buy F-35s.

"Whatever Canada's choice is we're going to be interoperable," said Work. "I mean Canada and the United States armed forces are as about as interoperable as you can imagine."

Canadian trainers could land on front lines in Iraq, Syria

That close relationship also exists in the U.S.-led coalition against ISIS in Iraq and Syria, Work said.

He told Barton that Canada will be "central" in training local ground troops who will lead the combat against ISIS in two key cities, Al-Raqqah in Syria, and Mosul in Iraq.

Last month Canada announced it will triple the number of Canadian Forces members helping to train local ground troops. The Communications Security Establishment, Canada's electronic spy service, is also set to play a more prominent role in the fight.

When pressed about any disappointment with Canada's decision to pull its jets out, Work shook his head "no."

Libyan troops sit on an armoured personnel carrier in August 2015 in Benghazi. Libya's second-largest city has seen some of the worst fighting since the 2011 uprising against Moammar Gadhafi. (Abdullah Doma/AFP/Getty Images)

He said the intelligence Canada provides "is just as important as six fighter jets."

Work, who previously worked as undersecretary of the U.S. navy, said it's hard to say whether Canada's decision to pull its six CF-18 jets out of the bombing mission will put people on the ground at risk.

"All of the pilots who fly over Iraq and Syria are at risk every day. A lot of people focus on the airplanes, for example, and of the 66 countries in the coalition, Canada punches well above its weight," he said.

Work said it's possible Canadian troops could find themselves caught in an unexpected attack alongside Peshmerga forces.

"It's a chaotic environment, it's a very fluid battlefield. It's not like a normal battlefield with front lines. [ISIS] is very canny and very good, tactically proficient at what they do on the battlefield," he said.

Canada welcomed in Libya campaign

The coalition is also trying to figure out the best way forward in Libya, a country disturbed by civil war and mounting Islamic extremism.

Work said he expects Canada to play an important role if the coalition does decide to expand its campaign into Libya. He said things have to happen sooner rather than later.

"We would like to have a government [in Libya] we could work with. That's the most problematic part right now," said Work.

Defence Minister Harjit Sajjan has already signalled that Canada could soon join a military coalition to take on an estimated 3,000 ISIS fighters in the country.