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

Ambassador David MacNaughton's comments are the first revelation that the Trudeau government spoke 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.

MacNaughton says Canadian officials were trying to understand 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.

MacNaughton says the two sides offered a number of proposals for resolving the dispute, before Boeing broke off talks.