Boeing walked away from talks with Canadian officials aimed at resolving the American aerospace company’s trade dispute with Montreal-based Bombardier, Canada’s ambassador to the U.S. said Tuesday.

Ambassador David MacNaughton said the officials wanted to know why Boeing was picking a fight with Bombardier, since the two are not direct competitors.

Boeing has accused Bombardier of selling its CSeries passenger liners to U.S.-based Delta Airlines at an unfairly low price with help from government subsidies in Canada.

Speaking in St. John’s, N.L., where federal ministers are holding a cabinet retreat, MacNaughton said the two sides offered a number of proposals for resolving the dispute, before Boeing broke off talks.

“We had some proposals back and forth and then they walked away,” the ambassador said. “For whatever reason, they decided they weren’t going to continue to have discussions with us.”

A senior Boeing official told The Canadian Press this month the firm was concerned that Bombardier’s deal with Delta could hurt its long-term prosperity and that of the entire aerospace sector.

MacNaughton’s comments are the first revelation that the Trudeau government has spoken directly with Boeing about the dispute, which has become a flashpoint for the Liberals.

They also come as media reports say British Prime Minister Theresa May, who will visit Canada next week, defended Bombardier during a recent call with U.S. President Donald Trump.

A senior government official speaking on background confirmed May’s planned visit on Sept. 18 and that the dispute between Bombardier and Boeing is expected to be raised.

Bombardier has a large aerospace facility in Belfast, the capital of Northern Ireland, which employs 4,200 people. It has several operations in other parts of the U.K., as well.

Foreign Affairs Minister Chrystia Freeland and MacNaughton spoke to the U.K. government about Bombardier on two separate occasions, the ambassador said, without providing details.

The dispute between Boeing and Bombardier has quickly escalated into a feud of epic proportions.

The U.S. Commerce Department is investigating Boeing’s complaint and preliminary findings are expected to be released on Sept. 25. The decision could lead to fines or tariffs against Bombardier.

The Liberal government has linked the trade dispute to its plan to purchase Super Hornet fighter jets by threatening to walk away from the deal if Boeing doesn’t drop the case.

Prime Minister Justin Trudeau also complained about subsidies to Boeing in a call with the governor of Missouri, where the Super Hornets are built.

Meanwhile, several U.S. members of Congress have come out in favour of Bombardier and urged the Trump administration to consider the Canadian company’s links to jobs south of the border.

But Boeing has shown no signs of backing down; Marc Allen, the president of Boeing’s international division, said this month that it wants to ensure a level playing field for all aerospace companies.

– With files from Sue Bailey in St. John’s.