The leaders of Fianna Fáil and the SDLP will announce details on Thursday of a formal partnership agreed between the parties.
Tonight, the Fianna Fáil parliamentary party was briefed in Leinster House about the details of the partnership that will be announced in Belfast.
It follows ongoing talks between the two parties that got under way last summer.
Both parties will retain their independence under this new arrangement, but will work together on all-island policy initiatives.
It means that Fianna Fáil will not run candidates in Northern Ireland and those running for the SDLP will not have Fianna Fáil branding on their election literature.
However, Fianna Fáil TDs may canvass for SDLP candidates in Northern Ireland.
The parties are also set to host joint conferences as part of this new alliance.
As I understand it - the @fiannafailparty and @SDLPlive Partnership means that both sides remain autonomous, while working together on a range of policies and issues of common concern. That’s opposed to a merger which would have meant only a single entity remained...— Paul Cunningham (@RTENewsPaulC) January 22, 2019