Dominic Raab has warned the "politicisation" of Northern Ireland issues by Brussels in Brexit trade talks is threatening the Good Friday Agreement.
The Foreign Secretary, following talks with US secretary of state Mike Pompeo, said he had made clear the UK's "absolute" commitment to the agreement.
The Government has come under fire from the EU over the UK Internal Market Bill which would allow ministers to override parts of the Brexit deal regarding trade with Northern Ireland.
Mr Raab, who is in Washington for talks with senior figures, said he had had "very positive discussions" with Republicans and Democrats.
He said: "It is a great opportunity to be clear that the threat to the Good Friday Agreement as it is reflected in the Northern Ireland protocol comes from the EU's politicisation of the issue, and to be clear on how that has happened and why that has happened."
"The UK action here is defensive in relation to what the EU is doing, it is precautionary, we haven't done any of this yet, and it is proportionate,” he said.
"What we cannot have is the EU seeking to erect a regulatory border down the Irish Sea between Northern Ireland and Britain."
Mr Raab will meet US House of Representatives speaker Nancy Pelosi later on Wednesday.
His comments came after Ms Pelosi warned Congress would never pass a free trade agreement with the UK if legislation to override the Brexit divorce settlement was to "imperil" the peace process.
