DUP leader Arlene Foster is to meet with the European Union's Chief Brexit Negotiator in Brussels.
She is expected to use the meeting with Michel Barnier to outline why her party opposes Theresa May's Withdrawal Agreement.
Mrs Foster will be joined by DUP MEP Diane Dodds as well as Conservative MPs Iain Duncan Smith and Owen Patterson at 11.30am on Thursday.
Speaking ahead of the meeting, Mrs Foster said she urges Mr Barnier to "acknowledge the concerns of those [they] represent in Northern Ireland."
She said, "We want to see a sensible deal which works for every part of the United Kingdom and respects the referendum result.
"However, we cannot settle for a deal which would undermine the economic and constitutional integrity of the United Kingdom."
Mrs Foster has also criticised Theresa May for her "weak approach" to Brexit negotiations which "demeans the strength of this great nation."
She continued, "It is also foolish as it traps the UK and burdens future generations with a bad deal."
Sinn Féin MEP Martina Anderson also met with Mr Barnier on Wednesday.
Joined by fellow MEP Matt Carthy, Mrs Anderson told the EU's Chief Brexit Negotiator that the EU needs to ensure the Good Friday Agreement is protected in its entirety.
Speaking after her meeting, the MEP said, “As the clock ticks closer to a disastrous crash-out Brexit, I made it clear to Michel Barnier and his team that the north cannot be allowed to become collateral damage to the reckless Tory Brexit agenda.
“The EU has a responsibility to ensure the Good Friday Agreement is protected that there will be no hardening of the border – something that would be totally unacceptable, particularly to those living in border communities."