The Foreign Affairs Committee in the US House of Representatives has unanimously passed a resolution reaffirming support for the Good Friday Agreement.
It means the bill will now advance to the full house for a vote at a future date.
The bipartisan resolution is co-sponsored by Democratic Congressman Thomas Suozzi and Republican Congressman Peter King and calls for strict adherence to the Good Friday Agreement during Brexit negotiations.
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.
Mr Suozzi said he hoped the legislation would be passed by the House of Representatives in short order.
"During these difficult times of often partisan and divided government in the United States, it is gratifying to see such overwhelming bipartisan support to ensure that Brexit and other political challenges don't threaten the Good Friday Agreement and the peace process by reintroducing a hard border," he said.
A similar resolution opposing the return of a hard border was introduced in the US House of Representatives in January.
Democratic Congressman Brendan Boyle was behind the move, saying that now was the time for the US Congress to make it clear that it stands in strong opposition to a hard border.
A number of senior members of the US Congress have warned that they will oppose any US-UK trade deal that undermines the Good Friday Agreement.
Those who have voiced their opposition include the Speaker of the House Nancy Pelosi, the Senate Minority Leader Chuck Schumer and the Chairman of the House Ways and Means Committee Congressman Richard Neal.