A US government official who warned the prime minister not to act unilaterally over the NI Protocol met Stormont political parties on Monday.
Derek Chollet, counsellor with the US Department of State, first met Northern Ireland Secretary Chris Heaton-Harris.
Mr Chollet said the meetings were "useful and productive".
Talks between the UK and EU have restarted, but progress could take months rather than weeks.
Speaking after the meetings, Mr Chollet said: "Northern Ireland's political, economic, and social progress over the past two-and-a-half decades is a result of the courage of the region's decision-makers and its citizens.
"I left in no doubt that its political leaders have the capacity and will to find agreed solutions to their political challenges.
"As a friend and partner, the United States will continue to underscore the importance of the Belfast/Good Friday Agreement and support all who seek to fulfil Northern Ireland's great potential".
He also passed on his condolences to Mr Heaton-Harris on the death of Queen Elizabeth II.
After meeting Mr Chollet, Mr Heaton-Harris said the United States and the UK shared a commitment to peace and prosperity in Northern Ireland and to upholding the Belfast (Good Friday) Agreement".
The US and the UK share a commitment to peace and prosperity in NI and to upholding the Belfast (Good Friday) Agreement. A pleasure to discuss shared priorities with Paul Narain @USAinNI and @CounselorDOS today.
Sinn Féin deputy leader Michelle O'Neill described Mr Chollet's trip to Northern Ireland as "significant".
"There is no doubt the US has political influence to bear, they have been very strong in making it clear that any breach of the Good Friday Agreement will mean no trade deal," she said.
"Ultimately all roads need to lead back to us being in the executive, people deserve no less."
On Saturday, Democratic Unionist Party (DUP) leader Sir Jeffrey Donaldson warned that his party would not return to a power-sharing executive and assembly at Stormont, until his demands were met on the protocol.
His party wants changes to reduce the number of checks on goods between Great Britain and Northern Ireland, saying the current situation threatens Northern Ireland's place within the UK.
The UK government has said it hopes a negotiated outcome can be reached with Brussels, which will have the DUP's backing.
Mr Heaton-Harris has said he will trigger a fresh Northern Ireland Assembly election if power-sharing is not restored by 28 October, the deadline in place under the existing law.
As well as meeting Ms O'Neill and Sir Jeffrey, Mr Chollet held private meetings with Alliance, the Ulster Unionists and the SDLP and also met assembly Speaker Alex Maskey as well as leaders from business and industry.
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