Northern Irish farmers fear an immediate loss of trade with the Republic could put hundreds of them out of business overnight.
Damian McGenity, a part-time farmer from Jonesborough, one mile on the northern side, says the economic impact would be “catastrophic”.
He explained: “An enormous amount of the commerce that happens in Northern Ireland happens because a product is made in the north, it’s shipped to the south, it comes back to the north and vice versa.
“I think 75% of the business activity that happens in Northern Ireland happens via a cross-border element.”
Dairy farmers are particularly concerned at the lack of breakthrough at this late stage.
An estimated 35% of the milk produced in Northern Ireland enters the Republic. If there is no deal by Friday, it will be prohibited from entering on Saturday.
Drivers who criss-cross the border, to collect milk from both sides in the same tanker, will be restricted to the southern side. The northern milk would no longer be EU regulated.
The Irish government says it is discussing options for the border with the EU. The British government says nothing needs to change but many doubt that.
Dr Katy Hayward, from Queen’s University Belfast, told Sky News: “It’s all very well to say you’re not going to impose any checks or controls but the fact is with a no-deal situation, you will have a customs border and a regulatory border.
“Those rules exist for a reason so customs controls protect citizens and consumers and if the UK wants to go and make deals with other countries, it has to be shown to be a responsible state.
There was always potential for Brexit to have an impact on the UK’s only land border with the EU but there was just as much potential for that border to have an impact on Brexit.
Whatever happens – no-deal, a further extension or something else – the need to avoid any visible partition on the island of Ireland is effectively shaping the UK’s departure from the EU.