OTTAWA -- Canada kicked the tires on the idea of buying used fighter jets from Kuwait to address a shortage of CF-18s, Defence Minister Harjit Sajjan revealed Thursday, but found they wouldn't be ready in time.

The revelation comes amid a bitter and escalating dogfight between U.S. aerospace giant Boeing and Montreal-based Bombardier, which has the backing of Justin Trudeau's federal Liberal government.

The Liberals had planned to buy 18 Super Hornets from Boeing to fill what they claim is a critical shortage of fighter jets, but have since threatened to go elsewhere over the Bombardier dispute.

Boeing has accused Bombardier of selling its controversial CSeries commercial liners to U.S.-based Delta Air Lines at a significant discount, thanks to assistance from what it considers improper government subsidies.

The dispute took a turn this week when the Department of Commerce ruled Bombardier did indeed receive improper subsidies and proposed a whopping 219 per cent duty on any CSeries planes entering the U.S.

The penalties won't be official until the U.S. International Trade Commission rules next spring on whether the Bombardier-Delta deal actually hurt Boeing's business.

The ruling has nonetheless divided the country -- advocates in Quebec and Ottawa have been calling on the Liberals to fight fire with fire, while officials in Manitoba, where Boeing has a large facility, are urging calm.

Speaking from Riga, Latvia, where Canada has about 450 soldiers helping guard against Russian aggression in the region, Sajjan said he was disappointed with the Commerce Department's ruling.

The minister wouldn't say explicitly that the plan to buy Super Hornets is officially off the table, but he suggested as much.

"We are going to be moving ahead with filling that capability gap," Sajjan said. "We are pursuing other options."

There are growing signs that the top option could be to buy used F/A-18s from Australia, which is getting rid of the fighter jets as it upgrades to the controversial F-35 stealth aircraft.

Kuwait, too, plans to sell its own used F/A-18s after securing its own deal to buy Super Hornets. There had been speculation the aircraft, which are similar to Canada's CF-18s, would be in good shape.

But Kuwait won't be ready to sell fast enough for Canada, Sajjan said, and the government is instead working closely with the Australians about possibly buying their jets.

"We have looked at the capability of the Kuwaiti fighters," Sajjan said.

"The biggest thing is right now they are not currently available. But we still want to pursue every single option. As you know, we are pursuing this option with the Australians at this time."

The key question appears to be whether any of Australia's F/A-18s have enough life left in them to serve alongside Canada's CF-18s until replacements for both begin to arrive in the mid-2020s.

The government has repeatedly emphasized the need for speed when it comes to addressing the current fighter-jet shortage, and hoped to buy interim Super Hornets by the end of the year.

That sense of urgency remains, Sajjan said, though he would not provide a timeline for when the government would pull the trigger on whatever option it decides to pursue.

"That capability we needed a long time ago," he said. "We had a plan in place, a very good plan that was going to fill the capability gap, invest in our current fleet and start the fighter replacement competition."

The government announced last November plans to purchase the planes to temporarily fill a critical shortage of fighter jets until the entire CF-18 fleet is replaced in the mid-2020s.

Many defence experts, including 13 former air force commanders, have questioned Liberal claims the air force doesn't have enough CF-18s, and said replacement jets could be purchased much faster.

The Boeing-Bombardier dispute has become a major international battle, with the Trump administration backing the former and the Canadian and British governments siding with the latter.

Bombardier has a large aerospace manufacturing facility in Northern Ireland.

Yet it has also pitted different parts of Canada against each other.

Quebec Premier Philippe Couillard, whose government invested $1 billion into the CSeries line, angrily called for a ban on all Boeing imports into Canada after the Commerce Department ruling.

But Manitoba Premier Brian Pallister and Winnipeg Mayor Brian Bowman called for cooler heads on Thursday, and said such rhetoric is not helpful.

Winnipeg is home to a Boeing manufacturing facility that employs 1,400 people and is the third biggest aerospace centre in the country.

-- with reporting by Chinta Puxley in Edmonton and files from Steve Lambert in Winnipeg