BELFAST - Britain's defence secretary on Wednesday warned that a trade challenge taken by Boeing (BA.N) against Canadian rival Bombardier (BBDb.TO) could jeopardise the U.S. firm's relationship with Britain, one of its biggest defence clients.

The U.S. Commerce Department on Tuesday imposed an anti-subsidy 220-per cent duty on the Bombardier's CSeries jets, whose wings are made at a Belfast plant that is Northern Ireland's largest manufacturing employer, following a complaint by Boeing.  

"This is not the behaviour we expect from Boeing and it could indeed jeapordise our future relationship with them," British Defence Secretary Michael Fallon told reporters in Belfast.

"Boeing has significant defence contracts with us and still expects to win further contracts. Boeing wants and we want a long term partnership but that has to be two way."