Liz Truss is resisting pressure from a close ally of Joe Biden not to rewrite the Brexit deal’s Northern Ireland protocol, saying she will not let the impasse “drag on”. The foreign secretary is facing concerted pressure from senior US politicians on the issue. Nancy Pelosi, the speaker of the House of Representatives, has already warned that she could endanger any hopes of a free trade deal with America. The protocol, which is part of the 2019 divorce treaty with the European Union, was designed to avoid placing a trade and customs border across the island of Ireland, instead placing it in the Irish Sea. Unionists say this undermines Northern Ireland’s position in the UK and Downing Street is threatening to unilaterally change or even dump the protocol. Truss was confronted yesterday by a delegation led by congressman Richard Neal, a senior Biden ally. There are concerns in Washington about tensions between London and Brussels and the impact on the Good Friday agreement if the British government goes ahead with its threats. However, it is understood that Truss said she was “defending the Good Friday agreement” rather than endangering it. She is understood to have said the protocol was having a severe impact and she could not let the “situation drag on” if the EU did not produce a reasonable solution. Business groups in Northern Ireland dispute that there is a problem, and have suggested that while the arrangements did cause disruption early on they are now cushioning the region from the impact of Brexit. Neal brought a delegation from the powerful congressional ways and means committee to Truss’s country retreat at Chevening in Kent. He had earlier held talks with EU officials in Brussels and had met Keir Starmer, the Labour leader. The meeting came just days after Truss declared that she had a plan for reworking parts of the protocol if a negotiated solution with the EU failed. The impasse has intensified after the DUP refused to take part in Northern Ireland’s power-sharing administration unless major changes were made to the way the Brexit deal was operating. Pelosi’s intervention, warning Boris Johnson that the protocol was necessary to maintain the peace agreement in Northern Ireland, was followed by a warning from Derek Chollet, a senior adviser to the US secretary of state, Antony Blinken. He called on Britain to avoid a “big fight” with the EU and urged both sides to “refrain from unilateral acts”. Some Tory MPs say they have become confused about the government’s position on the Northern Ireland protocol, with suspicions that a divide is opening up between Truss, who wants to take an aggressive approach, and some in Downing Street who are thought to be more wary of causing a major row with the EU, Dublin and Washington. Conor Burns, a Northern Ireland minister, has been appointed a special envoy for the Northern Ireland protocol in the US. He travelled to Washington earlier this month to have “candid” discussions with his American counterparts. There are hopes in Dublin and Washington that Truss’s threats are simply a negotiating tactic. Her plan includes the introduction of a “green channel” that would allow some goods to pass without checks from Great Britain to Northern Ireland, on the condition that they do not end up in the Republic of Ireland. It would give the UK more powers to change VAT in Northern Ireland. However, the EU believes the arrangement is inherently risky. So far, the EU has refused to allow any talks over reopening the protocol, instead offering a package to free up trade with the province.