Sinn Féin leaders are due to hold Brexit talks with Jeremy Corbyn in London.
Party president Mary Lou McDonald says she’ll tell the Labour leader that Irish interests must be protected, whatever the outcome of his negotiations with the Prime Minister.
Sinn Féin will also hold meetings with Secretary of State Karen Bradley.
Meanwhile the EU’s chief Brexit negotiator, Michel Barnier, will be in Dublin to meet with Taoiseach Leo Varadkar.
They will discuss the latest Brexit developments.
It comes ahead of an EU27 meeting on Wednesday, when European leaders will discuss Theresa May's request for a further extension.
Mr Varadkar has said his own preference was for a longer extension than the 30 June date proposed by the UK.