The EU's chief Brexit negotiator has said that the EU will consider "any solution" on Brexit which would allow it to maintain the integrity of the Belfast Agreement.
Michel Barnier said that it was important to maintain relationships in Northern Ireland.
Mr Barnier met with business leaders and cross-border groups at the Guildhall in Londonderry on Tuesday.
He was speaking as part of his two-day visit to Ireland.
Michel Barnier said he had come to listen to the views of people living and working in the North west.
"The Prime Minister has accepted with us to recognise that we have to work together to maintain the peace process.
"Now we have to find together the operational and practical solution," he said.
He said he was also delighted to be in this "vibrant and historical city" and he enjoyed a walk on the peace Bridge.
The DUP MLA Gary Middleton has criticised the lack of unionist representation at the meeting.
The European Commission office said that DUP MEP Diane Dodds had been invited.
The president of Londonderry Chamber of Commerce, Jennifer McKeever, said it was an incredible opportunity to have a conversation with Mr Barnier.
"He said he was very aware of the exceptional circumstances that we have here.
"He agreed that we need some rigorous framework going forward."
Mr Barnier gave a speech at an Irish government event in Dundalk on Monday before crossing the border to meet with business groups in Newry.
He said it had been "very useful and very interesting" to meet them.
Last week David Davis made an unannounced visit to the border area, spending a few hours in County Armagh.