Donald’s Trump special envoy to Northern Ireland has warned of the risk of creating a hard “border by accident” on the island of Ireland, as Boris Johnson’s newly drafted plan to rewrite the withdrawal agreement was rejected again by the EU. Mick Mulvaney, who was appointed by the US president in March, admitted to concerns about recent developments, including government legislation that could unilaterally override aspects of the agreement on Northern Ireland struck with Brussels last year. “Everyone assures me that no one is interested in seeing a hard border between the republic and Northern Ireland,” the former acting White House chief of staff said in an interview with the Financial Times. “We appreciate that, we respect that and we agree with that. The one thing I keep trying to assure is on the front of everybody’s mind is avoiding a border by accident. The Trump administration, state department and the US Congress would all be aligned in the desire to see the Good Friday agreement preserved to see the lack of a border maintained.” The comments follow a critical intervention by the Democratic presidential candidate, Joe Biden, after the UK government published its internal market bill and admitted it would breach international law. “We can’t allow the Good Friday agreement that brought peace to Northern Ireland to become a casualty of Brexit,” Biden tweeted. The speaker of the House of Representatives, Nancy Pelosi, has also warned that Congress will refuse to ratify any UK-US trade deal that comes before it if the British government fails to abide by the terms of the withdrawal agreement. Mulvaney said he had discussed the internal market bill with the Irish government and that he was closely monitoring the debate over it. His comments will be seen as all the more significant given they come from a Republican figure close to the White House. “I feel there’s so much left to be decided on Brexit including the [internal market bill]. I see nothing in particular that would inevitably lead to a hard border, but again I am simply concerned that everyone be aware of the potential risks,” he said. “We’re going to wait and see because the underlying EU-UK trade discussion could end up mooting the [internal market bill].” Under the withdrawal agreement, Northern Ireland will stay in the single market, including its state aid rules on domestic subsidies, and the full EU customs code will be enforced on goods crossing from Great Britain to Northern Ireland. This would require refundable tariffs to be paid on goods that are “at risk” of moving through Northern Ireland and on to the Republic of Ireland, if a wider “zero tariff, zero quota” trade deal between the EU and the UK is not struck this year. The internal market bill and an upcoming finance bill will give ministers the power to limit the reach of the EU’s state aid laws where they might go beyond Northern Ireland and impact on businesses in the rest of the UK from next year. Ministers would also be given the power to decide unilaterally what goods going from Great Britain to Northern Ireland would be judged to be “at risk” of moving into EU territory. The bill would additionally ensure that no export declarations were required for goods entering Britain from Northern Ireland. There are concerns that the failure of the UK to live up to its promise to enforce a regulatory and customs border in the Irish Sea could lead to the need for such checks to occur on the island of Ireland, a position that all sides are determined to avoid. Following an outcry by Tory MPs, Downing Street on Thursday clarified that it would only ask parliament to override parts of the Brexit agreement if the EU undermined the “fundamental purpose” of the Northern Ireland protocol. In the deal brokered with the rebels, the government said it would also seek to use the dispute resolution mechanisms in the withdrawal agreement at the same time as implementing the contentious clauses in the internal market bill. While some EU diplomats saw the government’s move as “promising”, senior EU officials close to the trade negotiations insisted the bill’s contentious clauses remained a breach of the withdrawal agreement. One such official said the UK was still seeking to negotiate “with a gun on the table – albeit not cocked”. “It’s better than more escalation. But … it’s trailing more breaches of the withdrawal agreement to come in the finance bill which is hardly reassuring.” One senior diplomat said the EU had been “distressed and appalled” by the UK’s attempt to unilaterally rewrite the withdrawal agreement but that the EU was determined to continue the talks. “Because it’s two separate tracks: one is the withdrawal agreement which the UK has decided to violate, and the next is going to be the future relationship,” the diplomat said. “We’ll see at the end of the month what the state will be then. We have several options at our hand on how to continue.” The EU is examining two main options: taking the UK to the European court of justice or continuing the negotiations and then presenting the British government with the choice of dropping the relevant clauses of the internal market bill in order to secure a trade deal or leaving without an agreement.