Representatives from Donegal and Derry Councils are travelling to Brussels for two days of intensive talks on Brexit.
They have been invited to the EU Parliament by MEP Mairead McGuinness as concerns deepen about the effects for Ireland.
The Vice President of the European Parliament has been examining the commitments made by both the EU and Britain over the Irish question.
"They've been made and signed up to by the European Union and they are really, determined, the European Union is very determined to ensure that the Irish question is addressed adequately and fairly," she said.
"I think the pressure ahs to come on the UK Government and Prime Minister, because she has also made a very strong political commitment that we will have no return to the past."