Further talks will be held later this week as the UK government continues to "press the case" on behalf of Bombardier workers in Northern Ireland, the British Business Secretary has said.
Thousands of Belfast posts hang in the balance if a proposed 300% duty on exports to the US is imposed on the Canadian-owned firm’s new C-Series jet.
British Business Secretary Greg Clark told MPs the Government was "absolutely determined to send a clear message both to Boeing and to the US administration that this action is unfair, its effects on Belfast are intolerable".
His comments came as DUP MP Gavin Robinson (Belfast East) raised the issue during Commons Business, Energy and Industrial Strategy (BEIS) questions, branding the US tariff situation "egregious".
He asked: "The Secretary of State may know that Unite the Union officials from Belfast Bombardier plant are in Washington and Montreal pressing the case against the egregious US tariff situation.
"Can the Secretary of State advise, is he continuing to engage in this process and working towards a sensible resolution?"
Mr Clark replied: "I certainly am and as he knows, throughout this process we’ve been absolutely determined to send a clear message both to Boeing and to the US administration that this action is unfair, its effects on Belfast are intolerable.
"I have further conversations later this week to continue to press the case with all of the parties concerned."
Earlier this month, trade unionists said a dispute between US planemaker Boeing and its Canadian rival Bombardier should be referred to the World Trade Organisation (WTO).
The plane’s wings are made in Northern Ireland and Unite the Union warned thousands of Northern Ireland jobs could be threatened should sales be badly affected.