Britain has insisted that it is up to the European Union to break the political deadlock in Northern Ireland, After assuring a delegation from the US Congress of its “cast-iron” commitment to peace in the province,

The UK government has sparked outrage on both sides of the Atlantic by proposing to revise the so-called Northern Ireland Protocol, a trading arrangement agreed as part of the UK’s Brexit divorce agreement with the EU.

London is attempting to appease pro-UK unionists who have refused to join a new power-sharing government in Belfast, which is being led for the first time by pro-Irish nationalists until the protocol is reformed.

Interviewed by the Sunday Telegraph newspaper, Northern Ireland Secretary Brandon Lewis demanded that Brussels adopt a new negotiating mandate to address the fierce objections of the Democratic Unionist Party (DUP).

“I made this point to the EU myself before the (May 5) elections. My view was, it was much easier to get a deal before the elections than afterwards,” Lewis said.

“The idea that it was going to be easier after the elections was a crazy one from the EU.”

The protocol recognised Northern Ireland’s status as a fragile, post-conflict territory that shares the UK’s new land border with the EU.

Keeping the border open with neighbouring Ireland, an EU member was mandated in the 1998 Good Friday Agreement, given that the frontier was a frequent flashpoint during three decades of violence.

But the protocol’s requirement for checks on goods arriving from England, Scotland and Wales has infuriated the DUP and other unionists, who say it drives a wedge between Northern Ireland and the rest of the UK.

Lewis stressed that the DUP, as the biggest unionist party, had a democratic mandate to back its position.

“And at the moment, the protocol, which the EU claims is about protecting the Good Friday Agreement, is the very document putting the Good Friday Agreement most at risk,” he said.

But the EU insists the protocol is not up for renegotiation.

And last week Nancy Pelosi, the speaker of the US House of Representatives, warned that the UK could forget about a post-Brexit trade deal if it rewrites the agreement.

On Saturday, Foreign Secretary Liz Truss met in England with a congressional delegation led by Richard Neal, a senior member of Pelosi’s Democratic party in the House.

“We discussed our cast-iron commitment to the Belfast (Good Friday) Agreement, the importance of free trade and our condemnation of Russia’s illegal invasion of Ukraine,” Truss tweeted.

The foreign ministry declined to comment further.

But according to Britain’s Observer newspaper on Sunday, Truss told Neal’s delegation that London could not let the “situation drag on” if the EU did not respond favourably.

After members of Congress visited Brussels on Friday, Neal emphasised Washington’s “unity” with the EU.

Following his “frank” meeting with Truss, the Democrat tweeted on Sunday, “I urge good faith negotiations with the EU to find durable solutions for post-Brexit trade between the United Kingdom and Northern Ireland.”