Theresa May has asked Donald Trump to help settle a trade dispute which could financially devastate one of Northern Ireland's biggest employers and put thousands of jobs at risk, following pressure from the DUP.
Canadian aerospace giant Bombardier, which employs around 4,500 people in Belfast and accounts for 10 per cent of the region's manufacturing exports, is embroiled in a spat with US aeronautics powerhouse Boeing.
The American company alleges Bombardier received unfair subsidies, including loans from the British and Canadian governments, which it claims allowed it to sell its CSeries planes at below-market prices.
The US Department of Commerce is expected to announce a decision on whether to impose punitative tariffs on Bombardier on 25 September.
The UK Government has been actively lobbying in the US for a compromise between the two companies amid growing concern about the potential implications for Bombardier's Belfast operations.
Punitative tariffs could mean Bombardier is unable to find customers for the CSeries planes in the US, putting the plant's future in doubt.
The Prime Minister is thought to have raised the matter with the US President in a phone call last week amid pressure from the Democratic Unionist Party (DUP), on whose support the Conservative government rely on to govern in Westminster.
“We have raised the issue at ministerial level,” DUP MP Sir Jeffrey Donaldson told The Guardian.
“We are aware that [Ms May] was involved at looking at the issue. And we would welcome it if she was talking to President Trump because Bombardier is a huge investor in Northern Ireland. We are very concerned at the current situation. Any intervention by her would be extremely welcome.”
Business Secretary Greg Clark also recently travelled to Boeing's base in Chicago to discuss the potential impact of the dispute and Northern Ireland Secretary of State James Brokenshire has been involved in negotiations.
Downing Street's involvement demonstrates the level of concern over the impact an adverse ruling by the US Department of Commerce against Bombardier could have on the future of the Northern Ireland factory.
Northern Ireland currently does not have its own functioning government. The Stormont Executive collapsed in January following a dispute between the two biggest parties, Sinn Fein and the Democratic Unionist Party (DUP).
Months of talks between the parties have failed to resolve the political crisis.
Around 1,000 of Bombardier's Belfast employees are involved in the making of the CSeries wings at the centre of the US-Canadian trade dispute.
Boeing filed a petition with the US International Trade Commission and the US Department of Commerce in April, alleging that massive subsidies from the Canadian government have allowed Bombardier to embark "on an aggressive campaign to dump its CSeries aircraft in the United States".
Bombardier has rejected Boeing's claims and said the US firm had not lost any sales as a result of Bombardier.
Industry sources told The Times that Mr Trump's "America first" rhetoric may have encouraged Boeing to take the action and said they doubted the White House would rein in the firm.
The Prime Minister raised the issue and her concern to protect jobs in Northern Ireland during a call with President Trump last Tuesday.
A Government spokesman said: "This is a commercial matter but the UK Government is working tirelessly to safeguard Bombardier's operations and its highly skilled workers in Belfast.
"Ministers across government have engaged swiftly and extensively with Boeing, Bombardier, the US and Canadian governments. Our priority is to encourage Boeing to drop its case and seek a negotiated settlement with Bombardier."
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