The US House of Representatives has voted in favour of a resolution reaffirming support for the Good Friday Agreement.
The bill, which calls for strict adherence to the Good Friday Agreement during Brexit negotiations, was passed by unanimous voice vote following a debate tonight on Capitol Hill.
The legislation urges the UK and the EU to ensure that Brexit does not threaten peace on the island of Ireland and strongly opposes the reintroduction of a hard border.
It also insists that any trade agreements between the US and the UK are contingent on meeting the Good Friday Agreement's obligations.
The bipartisan resolution was co-sponsored by Democratic Congressman Thomas Suozzi and Republican Congressman Peter King.
"The United States played an important role in the signing of the Good Friday Agreement, a momentous achievement that has been largely responsible for the relative peace over the last two decades," Congressman Suozzi said.
Republican Congressman Peter King also welcomed the passage of the resolution.
"It is imperative that the United States do all that it can to not only support the Good Friday Agreement but prevent any return of a hard border," he said.
The bill was unanimously passed by the House Foreign Affairs Committee in October.
A number of senior members of Congress had earlier warned that they would oppose any US-UK trade deal that undermines the Good Friday Agreement.
Those who had voiced their opposition include the House Speaker Nancy Pelosi, Senate Minority Leader Chuck Schumer, Chairman of the House Ways and Means Committee Congressman Richard Neal, and Democratic Congressman, Brendan Boyle.
Last month, former US vice-president Joe Biden voiced his support for protecting the Good Friday Agreement and avoiding a return to a hard border after Brexit.
Mr Biden, who is seeking the Democratic Party nomination for president, said he would continue to put pressure on the UK and that he has made it clear in the past that he does not support "breaking down" what is currently in place.