US diplomatic sources have issued a thinly veiled threat of a ban on Scottish salmon if Britain insists of blocking the import of American chlorinated chicken and hormone treated beef.
Scottish salmon is eagerly sought after by US consumers and exports are thought to be worth around £200-million a year – a tenth of total national output.
First Minister Nicola Sturgeon has promised to double Scottish salmon output by 2030.
Such a ban would not only hit the industry hard, but would further open the door for rival salmon producers such as Norway, Iceland and the Faroe Islands.
So far the threat has not come from any officially named sources but it is thought to have emanated from the US Embassy in London.
Scotch whisky and some home produced woollen products are already facing extra tariffs because of an ongoing row with the EU. Although the UK has officially left Europe, it is still recognised as being part of the union until the transition period ends on December 31st.
The Americans are likely to use environmental concerns such as salmon escapes of the type that took place recently after Storm Ellen, and biological problems such as salmon lice.
The warning has come through the Trump administration so much may depend on who wins the US Presidential election next month.
It is thought that Joe Biden, who is currently the clear favourite, might take a less strident approach. His prime concern is protecting the Northern Ireland Good Friday Agreement.
But he is still likely to face pressure from US beef and chicken farmers for tit-for-tat action if the British Government stands by its pledge to ban sub-standard food, all of which makes a UK-EU trade deal even more important.