The US House Speaker Nancy Pelosi warned that a unilateral UK legislation affecting the Northern Ireland protocol could endanger British prospects for a free trade deal with the US.
Pelosi's bluntly worded intervention came two days after Britain's foreign secretary, Liz Truss, confirmed that the government was planning to table legislation that would nullify parts of the protocol by exempting some goods moving between Great Britain and Ireland from EU customs checks.
Pelosi viewed the protocol as essential to the success of the Good Friday peace agreement of 1998, which minimized border controls between Northern Ireland and the Republic of Ireland.
The protocol for Northern Ireland was the result of negotiations with the EU on how to keep the frictionless border between the Irelands and maintain EU customs boundaries after Brexit.
If the United Kingdom is going to undermine the Good Friday accords, the Congress can't support a bilateral free trade agreement with the United Kingdom, as stated by the Speaker in a written statement. If the UK moves ahead with its legislation, the EU has warned of a potential trade war.
It is deeply concerning that the United Kingdom is now trying to renegotiate the Northern Ireland protocol, which preserves the important progress and stability forged by the accords. Pelosi said that it continues to enjoy strong bipartisan and bicameral support in the United States Congress.
The prime minister's special envoy for Northern Ireland Protocol in the US, Conor Burns, was in Washington to explain the UK position to the Biden administration and Congress, which is to blame the EU for inflexibility.
US officials were irritated that Burns, having emphasised his close relationship with Boris Johnson, had not warned them that Johnson was about to visit Northern Ireland. Burns assured them that no decision had been made on whether to pursue new legislation, days before Truss made her announcement.
Pelosi wrote on Thursday evening that I encourage constructive, collaborative and good-faith negotiations to implement an agreement that upholds peace. The children of Northern Ireland, who have never heard the bloody conflict and do not want to go back, deserve a future free of violence where all may reach their fulfillment.