DUP leader Arlene Foster has met with a representative group for loyalist paramilitaries over the Northern Ireland Protocol.
It comes amid anger among loyalists at new checks on goods arriving at ports, with claims an economic wedge has been driven between the region and the rest of the UK which undermines the Union.
Graffiti has appeared across Northern Ireland expressing opposition to a border in the Irish Sea.
Mrs Foster, along with her party’s deputy leader Nigel Dodds and East Belfast MP Gavin Robinson, discussed opposition to the protocol with the Loyalist Communities Council.
It represents loyalists groups including the UVF, UDA and Red Hand Commando.
A party spokesman said afterwards: “We listened to the views expressed and the need for political and constitutional methods to safeguard the United Kingdom single market and ensure there is an unfettered flow of trade between Great Britain and Northern Ireland.”
The DUP has urged the UK Government to ditch the protocol.
However, in a joint statement on Wednesday, UK Cabinet Office minister Michael Gove and European Commission vice president Maros Sefcovic said both sides are committed to the “proper implementation” of the protocol.
The protocol was designed by the EU and UK to avoid a hard border on the island of Ireland.
It achieves this by moving regulatory and customs checks to the Irish Sea, with goods imported into Northern Ireland from the rest of the UK subject to a range of new processes.
This has caused some disruption to trade since it came into effect on December 31, and those difficulties could intensify significantly on April 1 when a grace period currently limiting the bureaucracy applied to imported supermarket goods ends.