London (AFP) - Britain warned US aircraft giant Boeing on Wednesday that it risked government defence contracts worth billions with its challenge to Canadian rival Bombardier, which threatens thousands of jobs in Northern Ireland.
The US Commerce Department on Tuesday said it would impose anti-dumping duties of 220 percent on Bombardier's CSeries jets, following an investigation into state subsidies sparked by a Boeing complaint.
"This is not the behaviour we expect of Boeing and could indeed jeopardise our future relationship with Boeing," Defence Secretary Michael Fallon warned during a previously scheduled visit to Belfast.
Bombardier employs 4,200 people in aeronautics in Northern Ireland, centred around a Belfast factory that builds the CSeries wings and fuselage.
Thousands more work in the supply chain.
Prime Minister Theresa May's office earlier said it was "bitterly disappointed" by the preliminary ruling, but would keep working with the Canadian government and Bombardier to find a solution.
During a meeting last week at the United Nations in New York, May had personally lobbied US President Donald Trump to drop the case.
But Ross Murdoch, of the GMB union, accused her of being "asleep at the wheel when she could and should have been fighting to protect these workers".
Critics warned the ruling raised doubts about Britain's hopes of securing a quick trade deal with the United States when it leaves the European Union.
"Does not bode well for any UK US trade deal," tweeted Hugo Swire, a lawmaker in May's Conservative party and a former Foreign Office minister.
"We can't rely on a good trade deal with the US being agreed after Brexit," added pro-European opposition Labour lawmaker Conor McGinn.
"To protect jobs and our economy, we need to stay in the single market and customs union to preserve trade with our largest market -- the EU."
- 'Major defence partner' -
Canada has strongly protested the ruling, and stressed that duties can only be imposed once the final probe is completed, with a determination due on December 12.
This sentiment was echoed in London, where the government's business department said it was "only the first step in the process".
"We will continue to strongly defend UK interests in support of Bombardier at the very highest level because an adverse outcome risks jobs and livelihoods among the 4,200 skilled workers in Belfast," it said.
"Boeing's position in this case is unjustified and frankly not what we would expect of a long-term partner to the UK -- as well as damaging the wider global aerospace industry."
Fallon said Boeing was a "major defence partner", and stood to "gain a lot of British defence spending".
"We have contracts in place with Boeing for new maritime patrol aircraft and for Apache attack helicopters and they will also be bidding for other defence work," he said.
"And this kind of behaviour clearly could jeopardise our future relationship with Boeing."
In 2016, Britain announced a $2.3 billion deal to buy 50 Boeing Apache helicopters.
May is under particular pressure because of her deal with the Democratic Unionist Party (DUP), the largest party in Northern Ireland which is propping up her minority Conservative government in London.
"Obviously, we are very concerned about the jobs here in Belfast and Northern Ireland," DUP leader Arlene Foster told Sky News.
Noting May's recent meeting with Trump, she said: "We will use our influence with the government to make sure that that continues."