Brexit negotiators are due to discuss Northern Ireland issues in Brussels on Wednesday.
The UK and EU have agreed there will be no hard border, but are at odds on how to achieve that.
A major sticking point is what arrangement will be put in place if the border cannot be solved in an overall deal.
The two sides accept the need for this 'backstop' but differ on how it should work.
The arrangement, proposed by the EU, would mean Northern Ireland staying in the customs union and most of the single market.
The UK has firmly rejected that but has yet to present its own version of the backstop.
It has been reported that the British government will propose an arrangement that will apply to the UK as a whole and will cover at least customs arrangements.
The Irish government has made clear that a backstop which only deals with customs would not be enough to prevent a hardening of the border.
Wednesday's negotiations will be led by Olly Robbins, the prime minister's EU advisor, and Sabine Weyand, the EU's deputy chief negotiator.
Meanwhile, the president of the European Committee of the Regions, Karl-Heinz Lambertz, will visit the border on Wednesday as part of a fact-finding visit to Northern Ireland.
Facilitated by the Northern Ireland Local Government Association (NILGA), Mr Lambertz will visit the border prior to an engagement at the Flurrybridge Enterprise Centre, situated midway between Newry and Dundalk.