One of the United States' most influential politicians is visiting Ireland with a clear promise to help block any US-UK trade deal unless the Good Friday Agreement is protected.
Speaker of the US House of Representatives Nancy Pelosi is to visit the border region and make a historic address to the Oireachtas during her two-day visit.
Her comments are likely to be closely watched by US President Donald Trump with whom Ms Pelosi regularly clashes over policy and politics.
Ahead of coming to Ireland, Ms Pelosi and a delegation of congressmen held a series of high-level meetings with British politicians, including Labour leader Jeremy Corbyn.
And speaking at a London School of Economics event last night, she warned the US will not strike a wide-ranging trade deal with the UK after Brexit unless the threat of a hard border in Ireland is removed.
"We made it clear to all, If there is any harm to the Good Friday accord, no (trade) treaty," she said.
"I have to say though every single person, including Theresa May who we spoke to on the phone, everyone said don't even worry about that, it is unthinkable that we would even go there."
President Trump, a supporter of Brexit, has repeatedly said he is prepared to enter a “large scale” trade agreement with the UK.
During Taoiseach Leo Varadkar’s visit to the White House last month, the President was critical of the EU’s trading position but said he’d like “to see the whole situation with Brexit work out”.
“We can do a very big trade deal with the UK.” Separately, he tweeted: “My Administration looks forward to negotiating a large scale Trade Deal with the United Kingdom. The potential is unlimited!”
However, the Congress and members of Ms Pelosi’s Democratic Party will have a major say in any future trade deals.
In London she claimed the US missed an opportunity to gain economic leverage over China when it opted to put tariffs on the EU rather than join forces with it.
"I thought one of the biggest opportunities was for the US. and the EU to join together - the biggest market in the world, the two combined - and use that leverage in negotiations with the Chinese," Ms Pelosi said.
"So I wasn't pleased when the President put tariffs on the EU because you kind of started to weaken that strength vis-a-vis China."