British hopes of the United States lifting tariffs on steel and aluminum products imposed by former president Donald Trump have taken a hit because of Washington's concern about the impact of Brexit on the status of Northern Ireland.

Under the Brexit agreement last year, which was signed following the United Kingdom's exit from the European Union, Northern Ireland remained part of the EU's single market. This is something the London government now wants to change, less than a year after agreeing to it.

The potential for a hard border being introduced between Northern Ireland and the Republic of Ireland could potentially reignite decades of violent conflict known as the Troubles, which ended with the Good Friday Agreement in 1998.

The EU and US President Joe Biden have both repeatedly warned the UK about taking any action which might threaten peace in Ireland, and the Financial Times reported seeing documents making it clear that this is what is holding up talks.

In October, EU trade commissioner Valdis Dombrovskis said the bloc and the US had "paused" their dispute over the same tariffs, but the UK is out in the cold as it is no longer an EU member.

'Price for Brexit'

"This is yet another example of British industry paying the price for Boris Johnson's botched Brexit deal", said Stephen Kinnock, the opposition Labour Party's shadow foreign minister representing the steelmaking seat of Aberavon in Wales, to online news site Politico.

"Our economy and industry is paying the price for political and diplomatic failures. That's the bottom line of what's happening, and that is going to continue to be the case as long as Boris Johnson and Brexit Minister David Frost go around saber-rattling."

In correspondence seen by the Financial Times, a US Commerce Department official said there could be no progress over the matter, picking out the issue of Article 16, the legislation that relates to the suspension of the Northern Ireland Protocol, as the reason. The correspondence also stated that the government in London had been informed of this by Washington.

When asked about it by the Financial Times, the commerce department refused to comment, insisting the two sides were "consulting closely on bilateral and multilateral issues related to steel and aluminium", and the White House National Security Council has denied any connection between the Northern Ireland Protocol and trade talks. The UK's Department of Trade also rejected any link with the protocol.