ButCabinet Minister Michael Gove has said the government will ensure NI businesses will have "unfettered access" to the UK market after Brexit.
He met the leaders of all the devolved regions in Cardiff on Tuesday.
First Minister Arlene Foster and Deputy First Minister Michelle O'Neill raised concerns about the possibility of checks on goods crossing the Irish Sea.
Michel Barnier, said new checks on goods entering Northern Ireland from Great Britain are an "indispensable" consequence of the Brexit deal.
Secretary of State for NI."We will be in the UK customs union and we will be legislating to ensure unfettered access and we will deliver that," he said.