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ST. JOHN'S, Newfoundland (Reuters) - The leaders of Britain and Canada are set for talks next week on a crisis between Boeing Co BA.N and its Canadian rival Bombardier BBDb.TO that could have major political implications for both countries, a source close to the matter said on Tuesday.

The source, who declined to be identified because of the sensitivity of the situation, said Canadian Prime Minister Justin Trudeau and British counterpart Theresa May would meet in Ottawa on Sept. 18.

Boeing has launched a potentially damaging trade challenge action against Bombardier, alleging it is dumping its new C-Series passenger jets on the U.S. market.

Officials say both Britain and Canada are lobbying the U.S. Commerce Department to persuade Boeing to drop the challenge, which, if successful, could cripple Bombardier’s passenger jet division and cost thousands of jobs.

Bombardier is Northern Ireland’s largest manufacturing employer and May’s governing Conservatives depend on the support of a small Northern Irish party for their majority in parliament.

Bombardier is based in the Canadian province of Quebec, where Trudeau’s Liberals say they need to increase the number of Parliamentary seats to retain their majority in an election set for 2019.