The Democratic Unionist Party is to hold Brexit talks with Theresa May in Belfast on Wednesday.
Party leader Arlene Foster said she would tell the Prime Minister the proposed border backstop “drives a coach and horses through the Belfast Agreement’s principle of consent” and would effectively create a new border between Northern Ireland and the rest of the UK.
The party’s 10 MPs are opposed to the “insurance policy” contained in a proposed agreement with the EU which is designed to prevent the imposition of a hard Irish border after Brexit if no alternative trade deal is struck.
Mrs Foster said: “Parliament has spoken. A majority has rejected the current backstop.
“The European Union must now accept the need for the Withdrawal Agreement to be reopened. The toxic backstop must be dealt with.”
Mrs Foster said that the DUP wants “an orderly exit from the European Union which works for London, Dublin, Belfast and Brussels”.
She added: “It is possible but requires political will.
“This is not a time for intransigence. It is time to respect unionists and nationalists alike in Northern Ireland and deliver a deal which is sensible and practical.”
The DUP leader was “encouraged” by comments from EU Brexit negotiator Michel Barnier and Irish deputy premier Simon Coveney suggesting “a hard border can be avoided in any circumstance”.
“It is important that the scaremongering about barbed wire and checkpoints is exposed as nonsense.
“Border communities should not have genuine fears exploited with such tall tales.”
Sinn Fein president Mary Lou McDonald and deputy leader Michelle O’Neill will also meet Mrs May in Belfast.
The republican party supports the backstop as the “least worst option” to prevent what it fears would be significant disruption of all-Ireland trade following a disorderly UK exit from the EU.
It points out that a majority in Northern Ireland voted against Brexit.
Mrs O’Neill and party colleague Chris Hazzard met the Labour Party’s Brexit spokesman Keir Starmer on Monday to make it clear there can be no renegotiation of the backstop.
Ms O’Neill said: “We told him that the DUP do not speak for the people of the north and that the majority here did not consent to Brexit and do not want to be dragged out of the EU.
“The majority of political parties in the north continue to oppose Brexit and want to protect the Good Friday Agreement and prevent the return of a hard border.
“It is on that basis that the majority of political parties support the backstop.”