As Brexit threatens to cause turmoil across the European Union, perhaps no nation is feeling the strain of the United Kingdom’s 2016 referendum more than the Republic of Ireland. Three times now, U.K. Prime Minister Theresa May has failed to forge a compromise with the more conservative members of Parliament to ease the U.K. out of the E.U., and central to the debate is whether or not a customs border should be erected between northern and southern Ireland.

“We didn’t want to see Brexit happening, but it wasn’t our decision,” Daniel Mulhall, Ireland’s ambassador to the United States, said during an interview with Boston Public Radio on Monday. “From the Irish government’s point of view, the fundamental requirement is that there should be no possibility of a hard border on the island of Ireland anytime now or in the future.”

Mulhall says that while he respects the decision of the citizens of the U.K. to leave the E.U., he wants to ensure that it’s done in an “orderly” fashion that does not inflame tensions between Northern Ireland and the U.K. and possibly re-ignite sectarian violence that plagued the region between the late 1960s and '90s. In April, Northern Ireland was rocked by the murder of journalist Lyra McKee, who was mistakenly killed by Irish nationalists in the aftermath of a violent raid by U.K. police of a suspected weapons cache in Londonderry.

To Mulhall, incidents like the killing of McKee underscore how fragile the peace in the region is. He fears that erecting some form of a physical barrier will harken back to the darker days of mistrust, fear and violence that existed in Northern Ireland before the signing of the 1998 Good Friday Agreement.

“What we’re determined to do is to ensure that whatever happens in the future, there will never be a hard border on the island of Ireland,” Mulhall said. “We do not want to see customs posts being established because the risk is that if a customs post is established, someone will decide to attack that customs post, and then you could have an escalation of violence.”

As Brexit hardliners in London continue to pressure May with demands for a customs barrier on the Irish border, the Irish government has found an ally in some members of Congress. During a recent trip to Ireland, Speaker of the House Nancy Pelosi reaffirmed her support for the Good Friday Agreement, and floated the notion that a post-Brexit U.S.-U.K. trade deal would be at risk if the U.K. threatens the peace process in Northern Ireland.

“We must ensure that nothing happens in the Brexit discussions that imperils the Good Friday accord, including but not limited to the seamless border between the Irish Republic and Northern Ireland,” Pelosi said in front of a session of Irish Parliament on April 17. “If the Brexit deal undermines the accord, there will be no chance of a U.S.-U.K. agreement.”

Mulhall applauded Pelosi’s statements and said he’s also had positive conversations with members of the Trump administration who, he says, seem to be invested in maintaining peace in Ireland as well. Neither President Donald Trump or a representative of the administration have commented on Pelosi’s statements.

“It’s clear that some members of the administration have some sympathy for the Brexit project, but it’s also fair to say that they understand the importance of preserving peace in Ireland,” Mulhall said. “At this stage I have no complaints to make about the administration’s approach to the situation in Northern Ireland.”

Tensions may not bubble to a point where Pelosi will be forced to refuse a U.S.-U.K. deal, however. After April’s shooting, the U.K. government resumed talks to restore Northern Ireland’s devolved government, after more than two years without one, in an effort to restore peace.