(CNN) Some members of the US Congress have issued words of advice for the United Kingdom as it continues Brexit negotiations: Anything resembling a hard border between Northern Ireland and the Republic of Ireland, an EU member, will not be looked upon kindly.

Irish Deputy Prime Minister Simon Coveney's visit to Washington this week highlighted the problems the United Kingdom could face with future trade deals should members of Congress find issue with how the Brexit process plays out.

In an interview with CNN on Wednesday, Rep. Brendan Boyle, an Irish-American and member of the "Friends of Ireland" caucus that met with Coveney, said a hard border arising from Brexit negotiations would have a "major impact" on Capitol Hill.

"There's absolutely no way the US is going to do anything that would sacrifice our relationship with the EU," said Boyle, a Democrat from Pennsylvania. Congress would need to approve any future US-UK trade deals, he said.

"It's 2019 -- it's not the 1800s," he added. "And I think some people maybe sometimes forget that."

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